Broad specificity DNA damage endonuclease

ABSTRACT

The present disclosure describes DNA damage endonucleases which exhibit broad specificity with respect to the types of structural aberrations in double stranded DNA. These enzymes recognize double stranded DNA with distortions in structure, wherein the distortions result from photoproducts, alkylation, intercalation, abasic sites, mismatched base pairs, cisplatin adducts and inappropriately incorporated bases (for example, 8-oxoguanine, inosine, xanthine, among others). The UVDE (Uve1p) of  Schizosaccharomyces pombe , certain truncated forms of that UVDE (lacking from about 100 to about 250 amino acids of N-terminal sequence) and certain endonucleases from  Homo sapiens, Neurospora crassa, Bacillus subtilis , and from  Deinococcus radiodurans . The present disclosure further provides methods for cleaving double stranded DNA having structural distortions as set forth herein using the exemplified endonucleases or their stable, functional truncated derivatives.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority from U.S. Provisional Application No. 60/088,521, filed Jun. 8, 1998, and from U.S. Provisional Application No. 60/134,752, filed May 18, 1999.

ACKNOWLEDGMENT OF FEDERAL RESEARCH SUPPORT

This invention was made, at least in part, with funding from the National Institutes of Health (Grant Nos. CA 55896, AR 42687 and CA 73041), and the National Cancer Institute. Accordingly, the United States Government has certain rights in this invention.

BACKGROUND OF THE INVENTION

The field of the present invention is the area of DNA repair enzymes. In particular, the invention concerns the identification of stable ultraviolet DNA endonuclease polypeptide fragments, their nucleotide sequences and recombinant host cells and methods for producing them and for using them in DNA repair processes.

Cellular exposure to ultraviolet radiation (UV) results in numerous detrimental effects including cell death, mutation and neoplastic transformation. Studies indicate that some of these deleterious effects are due to the formation of two major classes of bipyrimidine DNA photoproducts, cyclobutane pyrimidine dimers (CPDs) and (6-4) photoproducts (6-4 PPs). (Friedberg et al. [1995] in DNA Repair and Mutagenesis, pp. 24-31, Am. Soc. Microbiol., Washington, D.C.).

Organisms have evolved several different pathways for removing CPDs and 6-4 PPs from cellular DNA (Friedberg et al. [1995] supra; Brash et al. [1991] Proc. Natl. Acad. Sci. U.S.A. 8810124-10128). These pathways include direct reversal and various excision repair pathways which can be highly specific or nonspecific for CPDs and 6-4 PPs. For example, DNA photolyases specific for either CPDs or 6-4 PPs have been found in a variety of species and restore the photoproduct bases back to their original undamaged states (Rubert, C. S. [1975] Basic Life Sci. 5A:73-87; Kim et al. [1994] J. Biol. Chem. 269:8535-8540; Sancar, G. B. [1990] Mutat. Res. 236:147-160). Excision repair has been traditionally divided into either base excision repair (BER) or nucleotide excision repair (NER) pathways, which are mediated by separate sets of proteins but which both are comprised of DNA incision, lesion removal, gap-filling and ligation reactions (Sancar, A. [1994] Science 266:1954-19560; Sancar, A. and Tang, M. S. [1993] Photochem. Photobiol. 57:905-921). BER N-glycosylase/AP lyases specific for CPDs cleave the N-glycosidic bond of the CPD 5′ pyrimidine and then cleave the phosphodiester backbone at the abasic site via a β-lyase mechanism, and have been found in several species including T4 phage-infected Escherichia coli, Micrococcus luteus, and Saccharomyces cerevisiae (Nakabeppu, Y. et al. [1982] J. Biol. Chem. 257:2556-2562; Grafstrom, R. H. et al. [1982] J. Biol. Chem. 257:13465-13474; Hamilton, K. K. et al. [1992] Nature 356:725-728). NER is a widely distributed, lesion non-specific repair pathway which orchestrates DNA damage removal via a dual incision reaction upstream and downstream from the damage site, releasing an oligonucleotide containing the damage and subsequent gap filling and ligation reactions (Sancar and Tang [1993] supra).

Recently, an alternative excision repair pathway initiated by a direct acting nuclease which recognizes and cleaves DNA containing CPDs or 6-4 PPs immediately 5′ to the photoproduct site has been described (Bowman, K. K. et al. [1994] Nucleic. Acids Res. 22:3026-3032; Freyer, G. A. et al. [1995] Mol. Cell. Biol. 15:4572-4577; Doetsch, P. W. [1995] Trends Biochem. Sci. 20:384-386; Davey, S. et al. [1997] Nucleic Acids Res. 25:1002-1008; Yajima, H. et al. [1995] EMBO J. 14:2393-2399; Yonemasu, R. et al. [1997] Nucleic Acids Res. 25:1553-1558; Takao, M. et al. [1996] Nucleic Acids Res. 24:1267-1271). The initiating enzyme has been termed UV damage endonuclease (UVDE, now termed Uve1p). Homologs of UVDE have been found in Schizosaccharomyces pombe, Neurospora crassa and Bacillus subtilis (Yajima et al. [1995] supra; Yonemasu et al. [1997] supra; Takao et al. [1996] supra). The Uve1p homologs from these three species have been cloned, sequenced and confer increased UV resistance when introduced into UV-sensitive strains of E. coli, S. cerevisiae, and human cells (Yajima et al. [1995] supra; Takao et al, [1996] supra). In S. pombe Uve1p is encoded by the uve1+ gene. However, because of the apparently unstable nature of partially purified full-length and some truncated UVDE derivatives, UVDE enzymes have been relatively poorly characterized and are of limited use (Takao et al. [1996] supra).

Because of the increasing and widespread incidence of skin cancers throughout the world and due to the reported inherent instability of various types of partially purified full-length and truncated UVDE derivatives, there is a long felt need for the isolation and purification of stable UVDE products, especially for use in skin care and medicinal formulations.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide purified stable UVDE (Uve1p), polypeptide fragments which retain high levels of activity, particularly those from the Schizosaccharomyces pombe enzyme. In a specific embodiment, the polypeptide fragment is Δ228-UVDE, which contains a 228 amino-acid deletion of the N-terminal region of the S. pombe uve1+ gene product; a second specific embodiment is the fusion protein GST-Δ228-UVDE. The DNA sequence encoding GST-full-length UVDE from S. pombe is given in SEQ ID NO:1. The deduced amino acid sequence of full-length GST-UVDE is given in SEQ ID NO:2. The DNA sequence encoding Δ228-UVDE is given in SEQ ID NO:3. The deduced amino acid sequence of Δ228-UVDE is given in SEQ ID NO:4. The DNA coding sequence and deduced amino acid sequence for GST-Δ228-UVDE are given in SEQ ID NO:5 and SEQ ID NO: 6, respectively. Also encompassed within the present invention are truncated UVDE proteins wherein the truncation is from about position 100 to about position 250 with reference to SEQ ID NO:2, and wherein the truncated proteins are stable in substantially pure form.

Also within the scope of the present invention are nucleic acid molecules encoding such polypeptide fragments and recombinant cells, tissues and animals containing such nucleic acids or polypeptide fragments, antibodies to the polypeptide fragments, assays utilizing the polypeptide fragments, pharmaceutical and/or cosmetic preparations containing the polypeptide fragments and methods relating to all of the foregoing.

A specifically exemplified embodiment of the invention is an isolated, enriched, or purified nucleic acid molecule encoding Δ228-UVDE. Another exemplified embodiment is an isolated, enriched or purified nucleic acid molecule encoding GST-Δ228-UVDE.

In a specifically exemplified embodiment, the isolated nucleic acid comprises, consists essentially of, or consists of a nucleic acid sequence set forth in SEQ ID NO:3 or SEQ ID NO:5.

In another embodiment, the invention encompasses a recombinant cell containing a nucleic acid molecule encoding Δ228-UVDE or GST-Δ228-UVDE. The recombinant nucleic acid may contain a sequence set forth in SEQ ID NO:3 or SEQ ID NO:5, a synonymous coding sequence or a functional derivative of SEQ ID NO:3 or SEQ ID NO:5. In such cells, the Δ228-UVDE coding sequence is generally expressed under the control of heterologous regulatory elements including a heterologous promoter that is not normally coupled transcriptionally to the coding sequence for the UVDE polypeptide in its native state.

In yet another aspect, the invention relates to a nucleic acid vector comprising a nucleotide sequence encoding Δ228-UVDE or GST-Δ228-UVDE and transcription and translation control sequences effective to initiate transcription and subsequent protein synthesis in a host cell. Where a GST full length or truncated derivative is expressed, the GST portion is desirably removed (after affinity purification) by protease cleavage, for example using thrombin.

It is yet another aspect of the invention to provide a method for isolating, enriching or purifying the polypeptide termed Δ228-UVDE.

In yet another aspect, the invention features an antibody (e.g., a monoclonal or polyclonal antibody) having specific binding affinity to a UVDE polypeptide fragment. By “specific binding affinity” is meant that the antibody binds to UVDE polypeptides with greater affinity than it binds to other polypeptides under specified conditions.

Antibodies having specific binding affinity to a UVDE polypeptide fragment may be used in methods for detecting the presence and/or amount of a truncated UVDE polypeptide in a sample by contacting the sample with the antibody under conditions such that an immunocomplex forms and detecting the presence and/or amount of the antibody conjugated to the UVDE polypeptide. Kits for performing such methods may be constructed to include a first container having a conjugate of a binding partner of the antibody and a label, for example, a radioisotope or other means of detection as well known to the art.

Another embodiment of the invention features a hybridoma which produces an antibody having specific binding affinity to a UVDE polypeptide fragment. By “hybridoma” is meant an immortalized cell line which is capable of secreting an antibody, for example a Δ228-UVDE specific antibody. In preferred embodiments, the UVDE specific antibody comprises a sequence of amino acids that is able to specifically bind Δ228-UVDE. Alternatively, a GST-tag specific antibody or labeled ligand could be used to determine the presence of or quantitate a GST-Δ228-UVDE polypeptide, especially in formulations ex vivo.

The present invention further provides methods for cleaving DNA molecules at positions with structural distortions, wherein the DNA is cleaved in the vicinity of the distortion by a stable truncated UVDE protein of the present invention. The structural distortion can result from mismatch at the site of the distortion in a double-stranded DNA molecule, from UV damage or from other damage to DNA due to chemical reaction, for example, with an alkylating or depurination agent or due to damage due to UV irradiation, ionizing radiation or other irradiation damage. The stable truncated UVDE proteins can be supplied in substantially pure form for in vitro reactions or they can be supplied for in vivo reactions, including but not limited to compositions for topical application (in the form or of an ointment, salve, cream, lotion, liquid or transdermal patch) in pharmaceutical compositions for internal use (to be administered by intraperitoneal, intradermal, subcutaneous, intravenous or intramuscular injection). The stable truncated UVDE derivatives of the present invention repair a wide variety of mismatch and DNA damage. The cleavage of a double stranded DNA molecule having structural distortion due to nucleotide mispairing (mismatch) or due to DNA damage by a stable truncated UVDE derivative of the present invention can be used to advantage in a relatively simple assay for structural distortion wherein cleavage of a test molecule (i.e., the double stranded DNA molecule which is being screened for damage, mismatch or other structural distortion) is to be detected.

The present invention further provides a method for cleaning a double stranded DNA molecule in which there is a structural distortion. The structural distortion can be due to aberrations including, but not limited to, base pair mismatch, photoproduct formation, alkylation of a nucleotide such that normal Watson-Crick base pairing is disturbed, intercalation between nucleotides of a compound which could be, for example, an acriflavine, an ethidium halide, among others, or a platinum adduct, for example of a cisplatin moiety. The DNA can also contain an abasic site, an inosine, xanthine, 8-oxoguanine residue, among others. The method of the present invention can be employed using the UVDE (Uve1p) protein from Schizosaccharomyces pombe, a truncated derivative of the S. pombe UVDE (lacking from about 100 to about 250 N-terminal amino acids), the Δ228-UVDE of S. pombe, or the Neurospora crassa, Bacillus subtilis, Homo sapiens or Deinococcus radiodurans enzymes as set forth herein (see SEQ ID NOs.:36-39). A specifically exemplified truncated UVDE (Δ228) is given in SEQ ID NO:4. DNA containing the structural distortion is contacted with an enzyme (or active truncated derivative) as described above under conditions allowing endonucleolytic cleavage of one strand of the distorted DNA molecule.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1C show purification and activity of GST-Δ228-UVDE and Δ228-UVDE. GST-Δ228-UVDE and Δ228-UVDE from overexpressing S. cerevisiae DY150 cells were purified by affinity chromatography on glutathione-Sepharose columns. FIG. 1A shows the purification of GST-Δ228-UVDE. Proteins were visualized on a silver-stained 12% SDS-polyacrylamide gel. Lanes M: protein molecular weight markers (sizes indicated on the right). Lane 1: 0.5 μg of soluble protein (column load) from crude extract of S. cerevisiae overexpressing cells. Lane 2: 0.5 μg of unbound protein from affinity column flow through. Lane 3: 1.0 μg of unbound protein from column wash fractions. Lanes 4-8: equal volume (20 μL) loads of column fractions from affinity column bound proteins eluted with glutathione corresponding to 5, 15, 65, 55, and 35 ng of total protein, respectively. FIG. 1B illustrates SDS-PAGE analysis (silver-stained 12% gel) of proteins following reapplication of GST-Δ228-UVDE onto glutathione-Sepharose and on-column thrombin cleavage to remove the GST tag. Lane M: protein molecular weight markers (sizes indicated on left). Lane 1: 100 ng of GST-Δ228-UVDE (column load). Lane 2: 250 ng thrombin reference marker. Lane 3: 250 ng of Δ228-UVDE eluted from column following thrombin cleavage. Lane 4: 400 ng (total protein, of GST-Δ228-UVDE and GST remaining bound to affinity column following thrombin cleavage and elution with glutathione. Arrows indicate the positions of GST-Δ228-UVDE (A, 68.7 kDa), Δ228-UVDE (B, 41.2 kDa), thrombin (C, 37 kDa), and GST (D, 27.5 kDa). FIG. 1C shows activities of GST-Δ228-UVDE and Δ228-UVDE preparations on CPD-30mer. CPD 30mer was incubated with the following preparations of UVDE: crude extract of overexpressing cell containing vector alone (lane 1), GST-Δ228-UVDE (lane 2), FL-UVDE (lane 3), affinity-purified GST alone (lane 4), affinity-purified GST-Δ228-UVDE (lane 5) and affinity-purified Δ228-UVDE (lane 6). Oligonucleotide cleavage products (14mer) corresponding to UVDE-mediated DNA strand scission of CPD-30mer immediately 5′ to the CPD site were analyzed on DNA sequencing gels and subjected to autoradiography and phosphorimager analysis.

FIG. 2 shows the effect of salt concentration on UVDE activity. DNA strand scission assays on end-labeled CPD-30mer were carried out with 150 ng of affinity -purified GST-Δ228-UVDE (open circles) or 40 ng of affinity-purified Δ228-UVDE (closed circles) at pH 7.5 and various concentrations of NaCl under otherwise standard reaction conditions for 20 min (Materials and Methods). Extent of DNA strand scission was determined from phosphorimagler analysis of gels. Enzyme activity is expressed as a percentage of CPD-30mer cleaved relative to that observed at 100 mM NaCl (defined as 100%).

FIG. 3 illustrates the effect of pH on UVDE activity. DNA strand scission assays on end-labeled CPD-30mer were carried out with 150 ng of affinity-purified GST-Δ228-UVDE (open circles) or 40 ng of affinity-purified Δ228-UVDE (closed circles) under various pH conditions at otherwise standard reaction conditions for 20 minutes (as described herein). Extent of DNA strand scission was determined from phosphorimager analysis of gels and enzyme activity is expressed as a percentage of CPD-30mer cleaved relative to that observed at pH 6.5 (defined as 100%).

FIG. 4 shows the temperature dependence of UVDE activity. DNA strand scission assays on end-labeled CPD-30mer were carried out with 150 ng of affinity-purified GST-Δ228-UVDE (open circles) or 40 ng of affinity-purified Δ228-UVDE (closed circles) at the indicated temperatures under otherwise standard reaction conditions (See the Examples herein below) for 20 minutes. Extent of DNA strand scission was determined from phosphorimager analysis of gels and enzyme activity is expressed as a percentage of CPD-30mer cleaved relative to that observed at 30° C. (defined as 100%).

FIGS. 5A-5B illustrates kinetic analysis of CPD-30mer cleavage by purified Δ228-UVDE. Δ228-UVDE (5 nM) was reacted with increasing amounts of 5′-end-labeled CPD-30mer and analyzed for DNA strand scission as described in the Examples. FIG. 5A is a plot of reaction rate (Rate) vs substrate concentration using the mean±standard deviation from three separate experiments. Curve shown is the best fit to the Michaelis-Menten equation of the averaged data. FIG. 5B is a Lineweaver-Burk plot of the kinetic data.

FIGS. 6A-6B show sites of Uve1p cleavage of CPD containing substrates. Various Uve1p preparations were incubated with 5′ or 3′ end-labeled (*) cs-CPD-30mer. Cleavage products corresponding to Uve1p-mediated strand scission of cs-CPD-30mer were visualized on a DNA sequencing-type gel. FIG. 6A: 5′ end labeled cs-CPD-30mer duplex was incubated with buffer only (lane 1), an extract of cells over-expressing GΔ228-Uve1p (5 μg) (lane 2), affinity-purified GΔ228-Uve1p (lane 3) and affinity-purified Δ228-Uve1p (50 ng of each) (lane 4) and affinity-purified GST alone (2 μg) (lane 5). FIG. 6B: 3′ end labeled cs-CPD-30 mer duplex was incubated with the same Uve1p preparations. Order of lanes is the same as for FIG. 6A. Arrows a and b indicate the primary and secondary cleavage sites. The photoproduct (T{circumflex over ( )}T corresponds to CPD) containing section of cs-CPD-30mer is shown at the bottom of the figure. For simplicity the complementary strand is not shown.

FIGS. 7A-7D demonstrate that GΔ228-Uve1p recognizes 12 different base mismatch combinations. The 3′ end labeled oligo series X/Y-31mer (sequence given at bottom, asterisk indicates labeled strand and labeled terminus) was utilized to assess Uve1p cleavage activity on 16 different base pair and base mispair combinations (Table 1B). Base mispairs indicated above numbered lanes with asterisks denoting base on the labeled strand for G-series (FIG. 7A), A-series (FIG. 7B), C-series (FIG. 7C) and T-series (FIG. 7D) treated with purified GΔ228-Uve1p (odd lanes) or mock reactions (even lanes). Reaction products were analyzed on DNA sequencing-type gels. Arrows indicate Uve1p cleavage sites immediately (arrow a), one (arrow b), and two (arrow c) nucleotides 5′ to the mismatch site. G and C+T base-specific chemical cleavage DNA sequencing ladders were run in adjacent lanes as nucleotide position markers.

FIGS. 8A-8E show Uve1p activity on bipyrimidine UV induced photoproducts. To determine if Uve1p was capable of recognizing a broad spectrum of UV induced photoproducts, crude extracts from cells expressing GΔ228-Uve1p (lane 1) and G-Uve1p (lane 2) (5 μg of each), and affinity-purified Δ228-Uve1p (lane 3) and GΔ228-Uve1p (lane 4) (50 ng of each) were incubated with the following 5′ end-labeled (*) duplex oligonucleotide substrates (FIG. 8A) cs-CPD-49mer, (FIG. 8B) 6-4PP-49mer, (FIG. 8C) tsI-CPD-49mer, (FIG. 8D) tsII-CPD-49mer, and (FIG. 8E) Dewar-49mer. The UV photoproduct (T{circumflex over ( )}T) containing section of the sequence is shown at the bottom of the figure. Arrows a and b indicate the major and minor products formed by Uve1p mediated cleavage. Arrow uc indicates the uncleaved substrate. The sequence of the complementary strand is omitted.

FIG. 9 shows Uve1p activity on a platinum-DNA GG diadduct-containing substrate. Affinity-purified GΔ228-Uve1p (lane 4) and A228-Uve1p (1-2 μg) (lane 5) were incubated with 5′ end-labeled duplex (*) Pt-Gg-32mer. This substrate was also incubated with buffer alone (lane 2), E. coli exonuclease III (150 units (Promega)) (lane 3) and affinity-purified GST (2 μg) (lane 6). Maxam and Gilbert sequencing (lane 1) of the oligonucleotide was carried out to identify the site of cleavage. Arrows c and d indicate the major and minor cleavage sites, respectively. The platinum-DNA GG diadduct containing section of the substrate is shown at the bottom of the figure. The sequence of the complementary strand is omitted.

FIG. 10A shows cleavage of an oligonucleotide substrate containing an AP site by Uve1p. To investigate if Uve1p was capable of cleaving an abasic site in a hydrolytic manner, we prepared a 5′ end-labeled (*) abasic substrate, AP-37mer, and incubated this substrate with buffer alone (lane 1), E. coli endonuclease III (AP lyase, lane 2), affinity-purified GΔ228-Uve1p and Δ228-Uve1p (2 μg) of each) (lanes 3 and 4), extracts of cells over-expressing GA228-Uve1p (5 μg) (lane 5), E. coli endonuclease IV (hydrolytic AP endonuclease, lane 6) and purified recombinant GST (2 μg) (lane 7). FIG. 10B demonstrates competitive inhibition of AP site recognition and cleavage. To demonstrate that the products generated are as a result of Uve1p-mediated cleavage at the AP site, AP-37mer was incubated with buffer alone (lane 1), E. coli endonuclease IV (lane 2), and affinity-purified GΔ228-Uve1p (2 μg) (lane 3) with 10× and 40× unlabeled cs-CPD-30mer (lanes 4 and 5, respectively) and 10× and 40× unlabeled UD-37mer (lanes 6 and 7, respectively). Arrows a and b indicate the primary and secondary Uve1p-mediated cleavage products, respectively. Arrow uc indicates the uncleaved substrate. A portion of the sequence of the AP substrate is shown at the bottom of the figure. S corresponds to deoxyribose and p corresponds to phosphate. The location of the cleavage sites of endonuclease III (E_(III)) and endonuclease IV (E_(IV)) are also indicated. For simplicity the complementary strand is omitted from the figure.

FIGS. 11A-11B characterize the Uve1 p-generated DNA strand scission products and activity of full-length Uve1p. FIG. 11A: Analysis of 5′ termini of Uve1p-generated DNA cleavage products with *CX/AY-31mer. 3′ end labeled oligo with C/A mismatch (sequence on bottom) reacted with GΔ228-Uve1p and then further treated with PNK or CIP as indicated in the (+) and (−) lanes. Lane 1 is buffer treatment only. Arrows a and b indicate sites of Uve1p cleavage. FIG. 11B: Full length Uve1p possesses mismatch endonuclease activity. 5′ end labeled duplex *CX/AY-31mer was incubated with crude extracts of cells expressing either full-length, GST-tagged Uve1p (GFL-Uve1p) (lane 1), truncated Uve1p (GΔ228-Uve1p) (lane 2), cells expressing the GST tag alone (lane 3) or with E. coil endonuclease V, a known mismatch endonuclease (lane 4). Arrows indicate cleavage sites immediately (arrow a) and one nucleotide 5′ to the mismatch site. Arrow V indicates E. coli endonuclease V cleavage 3′ to the mismatch site and was used as a position reference. Bands below arrows (indicated by asterisks) correspond to shortened products due to a weak 5′ to 3′ exonuclease activity present in the Uve1p preparations.

FIG. 12 shows that GΔ228-Uve1p mismatch endonuclease and GΔ228-Uve1p UV photoproduct endonuclease compete for the same substrates. GΔ228-Uve1p was incubated with 3′-end-labeled duplex *CX/AY-31mer (Table 1) in the presence of increasing amounts of unlabeled duplex CPD-30mer (squares) or duplex GX/CY-31mer (triangles) or duplex CX/AY-31mer (circles). The Uve1p-mediated DNA cleavage products were analyzed on DNA sequencing gels, and the extent of strand scission was quantified by PhosphorImager analysis. Uve1p activity is expressed as the percentage of the cleavage observed relative to that observed in the absence of any competitor (defined as 100% activity). The error bars indicate the mean±standard deviation from three separate experiments.

FIGS. 13A-13B show that Uve1p incises only one strand of a duplex containing a base mismatch. FIG. 13A shows 3′-end-labeled *CX/AY-41mer incubated with restriction enzyme DdeI (lane 1). GΔ228-Uve1p (lane 2), or buffer (lane 3). The reaction products were analyzed on a nondenaturing gel as described below for the presence of DNA double-strand break products (arrow dsb). Arrows b and c indicate the primary cleavage site for Uve1p on this substrate. FIG. 13B shows 3′-end-labeled *CX/AY-41mer or CX/*AY-41mer incubated with GΔ228-Uve1p (+lanes) or buffer (−lanes) and analyzed on denaturing DNA sequencing-type gels. Arrows b and c indicate positions of major Uve1p cleavage events relative to the mismatched base (asterisk) position. G+A and C+T base-specific sequencing ladders are included in outside lanes as nucleotide position markers.

DETAILED DESCRIPTION OF THE INVENTION

Abbreviations used in the present specification include the following: aa, amino acid(s); bp, base pair(s); BER, base excision repair; cDNA, DNA complimentary to RNA; CPD, cyclobutane pyrimidine dimer; FL, full-length; GST, glutathione-S-transferase; NER, nucleotide excision repair; PAGE, polyacrylamide gel electrophoresis; PMSF, phenylmethanesulfonyl fluoride, 6-4 PP, (6-4) photoproduct; UVDE or Uve1p, used interchangeably, ultraviolet damage endonuclease; Δ228-UVDE, UVDE truncation product lacking 228 N-terminal amino acids.

By “isolated” in reference to a nucleic acid molecule it is meant a polymer of 14, 17, 21 or more nucleotides covalently linked to each other, including DNA or RNA that is isolated from a natural source or that is chemically synthesized. The isolated nucleic acid molecule of the present invention does not occur in nature. Use of the term “isolated” indicates that a naturally occurring or other nucleic acid molecule has been removed from its normal cellular environment. By the term “purified” in reference to a nucleic acid molecule, absolute purity is not required. Rather, purified indicates that the nucleic acid is more pure than in the natural environment.

A “nucleic acid vector” refers to a single or double stranded circular nucleic acid molecule that can be transfected or transformed into cells and replicate independently or within the host cell genome. A circular double stranded nucleic acid molecule can be linearized by treatment with the appropriate restriction enzymes based on the nucleotide sequences contained in the cloning vector. A nucleic acid molecule of the invention can be inserted into a vector by cutting the vector with restriction enzymes and ligating the two pieces together. The nucleic acid molecule can be RNA or DNA.

Many techniques are available to those skilled in the art to facilitate transformation or transfection of the recombinant construct into a prokaryotic or eukaryotic organism. The terms “transformation” and “transfection” refer to methods of inserting an expression construct into a cellular organism. These methods involve a variety of techniques, such as treating the cells with high concentrations of salt, an electric field, or detergent, to render the host cell competent for uptake of the nucleic acid molecules of interest or liposome-mediated transfection can be employed.

The term “promoter element” describes a nucleotide sequence that is incorporated into a vector which enables transcription, in appropriate cells, of portions of the vector DNA into mRNA. The promoter element precedes the 5′ end of the Δ228-UVDE or GST-Δ228-UVDE nucleic acid molecule such that the Δ228-UVDE OR GST-Δ228-UVDE sequence is transcribed into mRNA. Transcription enhancing sequences may also be incorporated in the region upstream of the promoter. mRNA molecules are translated to produce the desired protein(s) within the recombinant cells.

Those skilled in the art would recognize that a nucleic acid vector can contain many other nucleic acid elements besides the promoter element and the Δ228-UVDE or GST-Δ228-UVDE nucleic acid molecule. These other nucleic acid elements include, but are not limited to, origins of replication, ribosomal binding sites, transcription and translation stop signals, nucleic acid sequences encoding drug resistance enzymes or amino acid metabolic enzymes, and nucleic acid sequences encoding secretion signals, periplasm or other localization signals, or signals useful for polypeptide purification.

As used herein, “Δ228-UVDE polypeptide” has an amino acid sequence as given in or substantially similar to the sequence shown in SEQ ID NO:4. A sequence that is substantially similar will preferably have at least 85% identity and most preferably 99-100% identity to the sequence shown in SEQ ID NO:4. Those skilled in the art understand that several readily available computer programs can be used to determine sequence identity with gaps introduced to optimize alignment of sequences being treated as mismatched amino acids and where the sequence in SEQ ID NO:4 is used as the reference sequence.

As used herein, “GST-Δ228-UVDE polypeptide has an amino acid sequence as given in or substantially similar to the sequence shown in SEQ ID NO:6. A sequence that is substantially similar will preferably have at least 85% identity and most preferably 99-100% identity to the sequence shown in SEQ ID NO:6. Those skilled in the art understand that several readily available computer programs can be used to determine sequence identity with gaps introduced to optimize alignment of sequences being treated as mismatched amino acids and where the sequence in SEQ ID NO:6 is used as the reference sequence.

By “isolated” in reference to a polypeptide is meant a polymer of 6, 12, 18 or more amino acids conjugated to each other, including polypeptides that are isolated from a natural source or that are chemically synthesized. The isolated polypeptides of the present invention are unique in the sense that they are not found in a pure or separated state in nature. Use of the term “isolated” indicates that a naturally occurring sequence has been removed from its normal cellular environment. Thus, the sequence may be in a cell-free solution or placed in a different cellular environment. The term does not imply that the sequence is the only amino acid chain present, but that it is essentially free (at least about 90-95% pure) of material naturally associated with it.

The term “purified” in reference to a polypeptide does not require absolute purity (such as a homogeneous preparation); instead, it represents an indication that the polypeptide is relatively purer than in the natural environment. Purification of at least two orders of magnitude, preferably three orders of magnitude, and more preferably four or five orders of magnitude is expressly contemplated, with respect to proteins and other cellular components present in a truncated UVDE-containing composition. The substance is preferably free of contamination at a functionally significant level, for example 90%, 95%, or 99% pure. Based on increases in calculated specific activity, GST-Δ228-UVDE and Δ228-UVDE have been purified 230-fold and 310-fold, respectively. However, based on silver-stained SDS polyacrylamide gel results, it appears that both proteins have been purified nearly to homogeneity (see FIG. 1).

As used herein, a “UVDE polypeptide fragment” or “truncated UVDE” has an amino acid sequence that is less than the full-length amino acid sequence shown in SEQ ID NO:2. Also used as used herein, UVDE and Uve1p are used synonymously.

In the present context, a “UVDE mutant polypeptide” is a UVDE polypeptide or truncated UVDE which differs from the native or truncated native sequence in that one or more amino acids have been changed, added or deleted. Changes in amino acids may be conservative or non-conservative. By conservative it is meant the substitution of an amino acid for one with similar properties such as charge, hydrophobicity and structure. A UVDE mutant polypeptide of the present invention retains its useful function, i.e., for example, ability to remove cyclobutane pyrimidine dimers and/or (6-4) photoproducts from DNA, and its enzymatic activity is stable in its substantially purified form. The full-length UVDE protein and the truncated derivatives of the present invention recognize a wide variety of DNA damage and distortions to double stranded DNA, as described hereinbelow. The UVDE and truncated UVDE proteins are useful in cleaving double-stranded DNA molecules in which damage including but not limited to abasic sites, photoproducts, cis-platin adducts and a variety of other aberrations also including mismatched base pairing and sites adjacent to and at locations of intercalations (for example with acridine dyes or ethidium bromide, among others, and these proteins, particularly the stable truncated derivatives of the present invention are useful in vivo and/or in vitro for repairing DNA distortions as described herein.

The isolation of genes encoding UVDEs from different organisms has been described previously (Yajima et al. [1995] supra; Takao et al. [1996] supra). These genes have been cloned by introducing a foreign cDNA library into a repair-deficient E. coli strain and selecting for complemented cells by UV irradiation of the transformants. (Yajima et al. [1995] supra; Takao et al. [1996] supra). Researchers have not characterized full-length UVDEs because they become unstable and lose their activity when purified (Takao et al. [1996] supra). This instability makes their use as therapeutic agents problematical.

Because UVDEs can be used for a variety of applications including the treatment and prevention of diseases caused by DNA damage, the inventors sought to discover stable UVDEs. The present inventors have noted that the activity of the full-length UVDE appears relatively stable to storage and freeze-thawing when it is present in crude extracts of either its native Schizosaccharomyces pombe or recombinant Escherichia coli (see also Takao et al. [1996] supra). The present inventors and others have not had success in obtaining enzymatically active purified UVDE in good yield. The present invention describes the isolation and purification of a polypeptide fragment from S. pombe which exhibits superior stability and enzymatic activity than purified full-length UVDE.

The full-length uvde gene from S. pombe was amplified from a cDNA library by the polymerase chain reaction (PCR) using methods known to those skilled in the art and as described herein. Δ228-UVDE, which contains a deletion of the of the first 228 N-terminal amino acids of full-length UVDE, was prepared using PCR as described herein.

The amplified UVDE gene coding fragments were cloned into the yeast expression vector pYEX4T-1. In pYEX 4T-1, the UVDE-derived polypeptides are expressed in frame with a glutathione-S-transferase (GST) leader sequence to generate a fusion protein of GST linked to the N-terminus of UVDE. The DNA sequence of the GST leader is shown in SEQ ID NO:7. The deduced amino acid sequence of the GST leader is shown in SEQ ID NO:8. Appropriate plasmids containing the DNA fragments in the proper orientation were transformed into S. cerevisiae, DY150 cells using the alkali cation method (Ito, H. et al. [1993] J. Bacteriol. 153:163-163). Positive clones were selected and used for protein purification.

Both full-length UVDE and Δ228-UVDE were isolated and purified using glutathione-Sepharose affinity chromatography. Extracts from cells expressing GST-Δ228-UVDE were passed through glutathione-Sepharose columns. GST-Δ228-UVDE which bound to the column was eluted using glutathione. Additionally, Δ228-UVDE was generated by removal of the GST-leader from GST-Δ228-UVDE by treating GST-Δ228-UVDE, which had bound to the glutathione-Sepharose column, with thrombin. Pooled fractions from the affinity purification yielded approximately 1.5 mg of near-homogeneous or homogeneous GST-Δ228-UVDE protein per 500 mL of S. cerevisiae cells.

GST-Δ228-UVDE and Δ228-UVDE have electrophoretic mobilities corresponding to protein sizes, is determined by SDS-PAGE, of 68.7 kDa and 41.2 kDa, respectively (FIG. 1A, lanes 4-8; FIG. 1B, lane 3). Both crude and purified preparations of Δ228-UVDE and GST-Δ228-UVDE retained enzymatic activity on an oligodeoxynucleotide substrate (CPD-30mer) containing a single cis-syn cyclobutane pyrimidine dimer embedded near the center of the sequence (FIG. 1C). In contrast, purified full-length UVDE resulted in a preparation that was not stable in that enzymatic activity was rapidly lost (FIG. 1C, lane 3). Furthermore, purified GST-Δ228-UVDE and Δ228-UVDE are stable when stored at −80° C. in 10% glycerol for a period of at least six months with no substantial loss of activity. Preparations of GST-Δ228-UVDE and Δ228-UVDE are resistant to several rounds of freeze-thawing. Surprisingly, both purified GST-Δ228-UVDE and Δ228-UVDE are more stable and have higher enzymatic activity than purified full-length UVDE.

Both truncated forms of UVDE (GST-Δ228-UVDE and Δ228-UVDE) retained high levels of activity over a broad NaCl concentration range (50-300 mM) with an optimum around 100 mM (FIG. 2). Optimal cleavage of an oligodeoxynucleotide substrate (CPD-30mer) occurred in the presence of 10 mM MgCl₂ and 1 mM MnCl₂. Both GST-Δ228-UVDE and Δ228-UVDE showed optimal cleavage of CPD-30mer at pH 6.0-6.5 with activity sharply declining on either side of this range indicating that the GST tag does not affect the folding and activity of the protein (FIG. 3). The calculated pI values for GST-Δ228-UVDE and Δ228-UVDE are 6.8 and 7.5, respectively.

Under optimal pH, salt and divalent cation conditions, GST-Δ228-UVDE and Δ228-UVDE were found to exhibit a temperature optimum at 30° C. (FIG. 4). At 37° C. GST-Δ228-UVDE and Δ228-UVDE activities decreased to approximately 85% and 60%, respectively and at 65° C., both truncated versions of UVDE showed a significant decrease in activity.

The kinetic parameters for homogeneous GST-Δ228-UVDE and Δ228-UVDE were determined using the CPD-30mer substrate. FIG. 5 shows that Michaelis-Menten kinetics apply to the CPD-30mer cleavage reactions with Δ228-UVDE. FIG. 5B is a Lineweaver-Burk plot of the kinetic data in FIG. 5A. The apparent K_(m) for CPD-30mer was calculated to be 49.1 nM±7.9 nM for GST-Δ228-UVDE and 74.9 nM±3.6 nM for Δ228-UVDE. The V_(max) values (nM min⁻¹) were found to be 2.4±0.13 and 3.9±0.12 for GST-Δ228-UVDE and Δ228-UVDE, respectively. The turnover numbers (K_(cat)) were 0.21±0.01 min⁻¹ for GST-Δ228-UVDE and 0.9±0.03 min⁻¹ for Δ228-UVDE.

Uve1p has been shown to be capable of recognizing both cis-syn CPDs (cs-CPD) and 6-4PPs (Bowman et al. [1994] Nucl. Acids Res. 22:3036-3032; Yajima et al. [1995] EMBO J. 14:2393-2399). It is unique in this respect as no other single polypeptide endonuclease is known to recognize both of these UV photoproducts. CPDs and 6-4PPs are the most frequently occurring forms of UV-induced damage, but there are significant differences in the structural distortions induced in DNA by these two lesions. Incorporation of a cs-CPD into duplex DNA causes no significant bending or unwinding of the DNA helix (Rao et al. [1984] Nucl. Acids Res. 11:4789-4807; Wang et al. [1991] Proc. Natl. Acad. Sci. USA 88:9072-9076; Miaskiewicz et al. [1996) J. Am. Chem. Soc. 118:9156-9163; Jing et al. [1998] supra; McAteer et al. [1998] J. Mol. Biol. 282:1013-1032; Kim et al. [1005] supra) and destabilizes the duplex by ˜1.5 kcal/mol (Jing et al. [1998] Nucl. Acids Res. 26:3845-3853). It has been demonstrated that this relatively small structural distortion allows CPD bases to retain most of their ability to form Watson-Crick hydrogen bonds (Jing et al. [1998] supra; Kim et al. [1995 9 Photochem. Photobiol. 62:44-50). On the other hand, NMR studies have suggested that 6-4PPs bend the DNA to a greater extent than cs-CPDs, and there is a destablization of ˜6 kcal/mol in the DNA duplex with a resulting loss of hydrogen bond formation at the 3′-side of the 6-4PP DNA adduct (Kim et al. [1995] Eur. J. Biochem. 228:849-854). The ability of Uve1p to recognize such different structural distortions suggests that it might also recognize other types of DNA damage.

CPDs can occur in DNA in four different isoforms (cis-syn I [cs I], cis-syn II [cs II], trans-syn I [ts I] and trans-syn II [ts II]) (Khattak, M. N. and Wang, S. Y. [1972] Tetrahedron 28:945-957). Pyrimidine dimers exist predominately in the cs I form in duplex DNA whereas trans-syn (ts) dimers are found primarily in single stranded regions of DNA. 6-4PPs are alkali labile lesions at positions of cytosine (and much less frequently thymine) located 3′ to pyrimidine nucleosides (Lippke et al. [1981] Proc. Natl. Acad. Sci. USA 78:3388-3392). 6-4PPs are not stable in sunlight and are converted to their Dewar valence isomers upon exposure to 313 nm light. We have investigated the specificity of Δ228-Uve1p for a series of UV photoproducts: cs-CPD, ts I-CPD, ts II-CPD, 6-4PP and the Dewar isomer. We also investigated the possibility that Uve1p may recognize other types of non-UV photoproduct DNA damage. We describe the activity of Uve1p on DNA oligonucleotide substrates containing a variety of lesions including a platinum-DNA GG diadduct (Pt-GG), uracil (U), dihydrouracil (DHU), 8-oxoguanine (8-oxoG), abasic sites (AP site), inosine (I), and xanthine (Xn). This collection of substrates contains base lesions that induce a broad range of different DNA structural distortions.

Uve1p isolated from S. pombe was first described as catalyzing a single ATP-independent incision event immediately 5′ to the UV photoproduct, and generating termini containing 3′ hydroxyl and 5′ phosphoryl groups (Bowman et al. [1994] Nucl. Acids Res. 22:3026-3032). The purified GΔ228-Uve1p, Δ228-Uve1p and crude cell lysates of recombinant G-Uve1p and GΔ228-Uve1p make an incision directly 5′ to CPDs similar to that observed with the native protein. In this study, we have used both 5″ and 3′ end-labeled duplex CPD-30mer (cs-CPD-30mer) to demonstrate the ability of Uve1p to cleave a CPD-containing substrate at two sites (FIGS. 6A-6B). The primary product (arrow a) accounted for approximately 90% of the total product formed and resulted from cleavage immediately 5′ to the damage. The second incision site was located one nucleotide upstream and yielded a cleavage product (arrow b), which represented the remaining 10% of the product formed. This minor product is one nucleotide shorter or longer than the primary product depending on whether 5′ or 3′ end-labeled substrate is being examined. The same cleavage pattern was observed for each different Uve1p preparation used: i.e., crude extracts of cells expressing GΔ228-Uve1p, affinity-purified GΔ228-Uve1p and Δ228-Uve1p (FIGS. 2A and 2B, lanes 2, 3 and 4 respectively), as well as extracts of cells expressing GST-Uve1p. No cleavage products were observed when the cs-CPD-30mer substrates were incubated with buffer only, or purified recombinant GST prepared and affinity-purified in an identical manner to the purified Uve1p proteins (FIGS. 6A, 6B, lanes 1 and 5 respectively). This control eliminates the possibility that these DNA strand scission products are formed as a result of the presence of trace amounts of non-specific endonuclease contamination. Uve1p recognizes a duplex cs-CPD-containing oligonucleotide substrate and cleaves this substrate at two sites. The primary site, responsible for 90% of the product, is immediately 5′ to the damage and the secondary site (accounting for the remaining 10% of product), is one nucleotide 5′ to the site of damage.

Uve1p cleaves both CPDs and 6-4PPs when they are incorporated into oligonucleotide substrates (Bowman et al. [1994] supra; Yajima et al. [1995] EMBO J. 14:2393-2399). These lesions induce substantially different distortions in duplex DNA. The ability of native Uve1p to recognize both of these damages prompted us to investigate whether this endonuclease recognized other forms of UV-induced photodamage, as well. In order to determine the substrate range of recombinant Δ228-Uve1p for UV-induced bipyrimidine photoproducts, various Uve1p preparations were incubated with synthetic 49-mer oligonucleotides containing different forms of UV damage (Table 1A). The substrates used in these experiments were 5′ end labeled duplex cs-CPD-49mer, tsI-CPD-49mer, tsII-CPD-49mer, 6-4PP-49mer and Dewar-49mer (FIG. 8A). Generally, purified GΔ228-Uve1p and Δ228-Uve1p cleaved all of the bipyrimidine photoproduct substrates in a similar manner with respect to both the site and extent of cleavage. The cleavage pattern observed when crude cell lysates of G-Uve1p and GΔ228-Uve1p were incubated with the substrates was less consistent. Very low levels of product were observed when these extracts were incubated with the Dewar isomer. No cleavage products were detected when the damaged substrates were incubated with buffer alone or purified recombinant GST, demonstrating that no other DNA repair proteins were responsible for the cleavage of the substrate. In addition, incubation of Uve1p with end-labeled undamaged substrate (UD-30mer) did not result in the formation of any cleavage products. We concluded that Uve1p recognizes and cleaves these five UV-induced bipyrimidine photoproducts in a similar manner and that they are substrates for this enzyme. This is the first time that a single protein endonuclease capable of recognizing such a surprisingly broad range of UV-induced photoproducts has been described.

To explore activity on DNA with non-UV-photoproduct diadducts we investigated whether Uve1p recognized an oligonucleotide containing a platinum-DNA lesion. cis-Diamminedichloroplatinum(II) (cisplatin) is a widely used antitumor drug that induces several types of mono- and diadducts in DNA. One of the major, biologically relevant adducts formed results from the coordination of N-7 of two adjacent guanines to platinum to form the intrastrand crosslink cis-[Pt(NH₃)₂{d(GpG)-N7(1)-N7(2))}](cis-PT-GG) (FIG. 9). A 5′ end-labeled duplex 32-mer oligonucleotide with a single platinum intrastrand crosslink between positions 16 and 17 (Pt-GG-32mer) (Table 1A) was incubated with either GΔ228-Uve1p or Δ228-Uve1p, and the reaction products were visualized on a DNA sequencing-type gel (FIG. 9). The 3′ to 5′ exonuclease activity of E. Coli exonuclease III was used to identify the specific site of cleavage of Uve1p, as a platinum-DNA diadduct will terminate or stall the digestion of the duplex DNA at this site (Royer-Pokora et al. [1981] Nucl. Acids Res. 9:4595-4609; Tullius, T. D. and Lippard, S. J. [1981] J. Am. Chem. Soc. 103:4620-4622). Incubation of 5′ end-labeled Pt-GG-32mer with exonuclease III (FIG. 9, lane 3) generates 5′ end-labeled oligonucleotide fragments with 3′ hydroxyl termini. Maxam and Gilbert sequencing (FIG. 9, lane 1) of the same substrate generates 5′ end labeled fragments with 3′ phosphoryl termini which consequently migrate faster than the exonuclease III product on DNA sequencing-type gels. (Due to overreaction with hydrazine all of the nucleotides are highlighted in the sequencing lane.) GΔ228-Uve1p cleaved Pt-GG-32mer 5′ to the GpG adduct position at two adjacent sites (FIG. 9, lane 4, arrows c and d). The products c) and d) migrate with the exonuclease III products, confirming that they have 3′ hydroxyl termini. Comparison with the Maxam and Gilbert sequencing ladder (FIG. 9, lane 1) indicates that the GΔ228-Uve1p-mediated cleavage products are generated by cleavage at sites located two and three nucleotides 5′ to the platinum DNA-GG diadduct. The GA228-Uve1p-mediated cleavage products were quantified by phosphorimager analysis, and it was determined that cleavage at the primary site c (arrow c) accounted for approximately 90% of the total product formed while cleavage at the secondary site (arrow d) accounted for the remaining 10%. In contrast, Δ228-Uve1p appeared to cleave Pt-GG-32mer only at the primary site c (i.e., two nucleotides 5′ to the damage) (FIG. 9, lane 5). When the quantity of protein used and the total amount of product formed is taken into account, the cleavage of Pt-GG-32mer by Uve1p appears at least 100-fold less efficient than the cleavage of the UV-induced photoproducts. Despite this significant decrease in efficiency, Pt-GG-32mer is a substrate for Uve1p, albeit a poor one, and more importantly, Uve1p is capable of recognizing and cleaving a non-UV photoproduct dimer lesion.

Uve1p is active on substrates containing non-bulky DNA damages. The ability of Uve1p to recognize and cleave non-UV photoproduct DNA diadducts prompted us to investigate whether other types of base damage could also be recognized by this versatile endonuclease. These damages included abasic sites (AP sites), uracil (U), dihydrouracil (DHU), inosine (I), xanthine (Xn) and 8-oxoguanine (8-oxoG) (Scheme 1C). For these studies, we utilized 37-mer oligonucleotide substrates with the damages placed near the center of the molecule and within the same DNA sequence context (Table 1B). These oligonucleotides, Ap-37mer, U-37mer, DHU-37mer and 8-oxoG-37mer were incubated with various Uve1p preparations, and the reaction products were analyzed on DNA sequencing-type gels. In addition,31 mer oligonucleotides containing inosine (I-31mer) and xanthine (Xn-31mer) were also tested as potential Uve1p substrates (Table 1A).

Abasic sites (AP sites) arise in DNA from the spontaneous hydrolysis of N-glycosyl bonds and as intermediates in DNA glycosylase-mediated repair of damaged bases (Sakumi, K. and Sekigachi, M. [1990] Mutat. Res. 236:161-172). AP endonucleases cleave hydrolytically 5′ to the site to yield a 3′hydroxyl termini, AP lyases cleave by a β-elimination mechanism leaving a 3′-αβ-unsaturated aldehyde (Spiering, A. L. and Deutsch, W. A. [1981] J. Biol. Chem. 261:3222-3228). To determine if Uve1p cleaves AP sites, we incubated affinity-purified GΔ228-Uve1p and Δ228-Uve1p and crude extracts of cells expressing GΔ228-Uve1p with a 5′ end-labeled oligonucleotide substrate containing an AP site placed opposite a G residue (AP/G-37mer). The products were analyzed on a DNA sequencing-type gel as before (FIG. 10A, lanes 3, 4 and 5 respectively). E. coli endonuclease III (which has an associated AP lyase activity) and E. coli endonuclease IV (a hydrolytic AP endonuclease) were used to determine if the cleavage products formed during incubation with Uve1p preparations were due to a β-elimination mechanism or hydrolytic cleavage (FIG. 10A, lanes 2 and 6 respectively). Uve1p recognized the AP site in this oligonucleotide substrate and cleaved it in a similar manner to E. coli endonuclease IV. Incubating the Uve1p proteins with an oligonucleotide substrate where the AP site was placed opposite an adenine residue (AP/A-37mer) resulted in no significant change in the amount of cleavage product formed. To further test Uve1p recognition of AP sites, we used unlabeled cs-CPD-30mer as a specific competitor for Uve1p. Addition of 40× unlabeled CPD-30mer to reactions of a 5′ end-labeled AP/(G-37mer with the purified GΔ228-Uve1p resulted in an −60% decrease in the amount of product formed. The addition of 40× unlabeled undamaged 30mer (UD-30mer) had no effect on the amount of product observed. Uve1p is capable of recognizing AP sites, and changing the complementary base has little or no effect on the extent of cleavage.

Uracil lesions can occur in DNA by the spontaneous deamination of a cytosine residue. Dihydrouracil is a pyrimidine photoproduct that is formed by the deamination of cytosine with subsequent ring saturation upon exposure to ionizing radiation under anoxic conditions (Dizdaroglu et al. [1993] Biochemistry 45:12105-12111). To determine if Uve1p recognized uracil and dihydrouracil lesions, we incubated various preparations of Uve1p with 3′ end-labeled 37mer oligonucleotides containing uracil and DHU residues placed opposite a G (U/G-37mer, DHU/G-37mer). The results of this set of experiments are summarized in Table 2. Purified GΔ228-Uve1p cleaved U/G-37mer and DHU/G-37mer in a typical Uve1p mediated fashion: immediately 5′ to the position of the lesion to form a major product, and again one nucleotide 5′ to the damaged site to form a minor product, 90% and 10% of the total Uve1p-mediated cleavage products, respectively.

Persistence of uracil and DHU lesions through replication may lead to the incorporation of adenine residues opposite the damaged base. To examine if Uve1p were equally efficient at recognizing uracil and DHU when they were base paired with an adenine residue, we constructed the substrates U/A-37mer and DHU/A-37mer. The results obtained from the analysis of Uve1p cleavage of these substrates are summarized in Table 2. No Uve1p mediated cleavage products were observed when crude extracts from cells expressing GΔ228-Uve1p and purified GΔ228-Uve1p were incubated with the U/A-37mer. Incubating purified GΔ228-Uve1p with DHU/A-37mer rather than DHU/G-37mer resulted in a 4-fold decrease in the amount of Uve1p-mediated cleavage products observed. To determine whether Uve1p, cleaves the complementary strand of these substrates (i.e., U/A-37mer, DHU/A-37mer or U/G-37mer, DHU/G-37mer), we conducted similar experiments with these substrates except that the complementary strand was 3′ end-labeled. No cleavage products were observed when these substrates were incubated with purified Uve1p protein preparations. Uve1p recognizes and cleaves uracil and DHU when they are placed opposite a G (U/G or DHU/G). However, when the lesions are placed in a situation where Watson-Crick hydrogen-bonding is maintained (U/A or DHU/A), Uve1p either fails to recognize the lesion completely (U/A) or the extent of cleavage is significantly decreased (DHU/G).

Uve1p recognizes and cleaves oligonucleotide substrates containing AP sites, uracil and DHU lesions. AP sites appear to be better substrates for Uve1p than uracil or DHU containing oligonucleotides; Uve1p cleaved AP sites at least 10 times more efficiently than uracil containing substrates and twice as efficiently as DHU containing substrates. However, they are all poorer substrates than UV-induced photoproducts. See Table 3 for a summary of the relative efficiency for cleavage by Uve1p on various substrates.

Additionally, the Uve1p preparations were incubated with the following substrates to determine if these lesions were capable of being cleaved by Uve1p: inosine and xanthine placed opposite a T or C (I/T-31mer, I/C-31mer and Xn/T-31mer, Xn/C-31mer), and 8-oxoguanine placed opposite all four bases (8-oxoG/G-37mer, 8-oxoG/A-37mer, 8-oxoG/T-37mer, 8-oxoG/C-37mer). No cleavage of either strand in these duplex substrates was observed.

As discussed hereinabove, because of substantial structural differences between CPDs and 6-4PPs, it was not obvious what features of damaged DNA Uve1p recognizes. One possibility is that Watson-Crick base pairing is disrupted for the 3′ pyrimidines in both CPDs and 6-4PPs (Jing et al. [1998] Nucl. Acids. Res. 26:3845-3853), suggesting that Uve1p might target its activity to mispaired bases in duplex DNA. We therefore investigated the ability of purified GΔ228-Uve1p to cleave duplex oligonucleotides containing all possible combinations of single base mispairs embedded within the same flanking sequence context. For these studies, we utilized a collection of mismatch-containing oligonucleotides (series XY-31 mer) which were designed so as to generate all possible mismatch combinations (Table 1B). Strands GX, AX, TX and CX were 3′ end-labeled and then annealed to strands GY, AY, TY or CY prior to incubation with purified GΔ228-Uve1p. Reaction products were analyzed on DNA sequencing-type gels (See Examples). The ability of GΔ228-Uve1p to cleave all twelve possible mispair combinations is shown in FIGS. 7A-7D. No DNA strand cleavage was observed for duplex substrates containing normal Watson-Crick G/C or A/T base pairs.

The sites of GΔ228-Uve1p-mediated mismatch-specific DNA cleavage were identified in each case by comparing the electrophoretic mobilities of the DNA strand scission products to those of a DNA sequencing ladder obtained by base-specific chemical cleavage. Arrows a, b, and c indicate the DNA strand scission products corresponding to cleavage by GΔ228-Uve1p immediately (position 0), one (position −1) or two (position −2) nucleotides 5′ to the site of the mismatch, respectively (FIGS. 7A-D). These sites of GΔ228-Uve1p-mediated endonucleolytic cleavage were confirmed in similar experiments employing 5′ end-labeled GX, AX, TX and CX strands in the mismatch substrates. In addition, the non-truncated, full-length GFL-Uve1p (in crude cell extracts) recognized and cleaved *CX-AY-31mer in a manner identical to GΔ228-Uve1p (FIG. 11B). The preferred sites of cleavage and the efficiency with which each mismatch is recognized by GΔ228-Uve1p is variable and depends on the type of base mispair that is presented to the enzyme. Within the sequence context examined, GΔ228-Uve1p exhibited strong cleavage at *C/C (asterisk-labeled strand base), *C/A and *G/G sites, moderate cleavage at *G/A, *A/G and *T/G sites, and weak cleavage at *G/T, *A/A, *A/C, *C/T, *T/T and *T/C sites. These differences in the extent of cleavage were reproducible and observed in three separate experiments. These results indicate that the GΔ228-Uve1p mismatch endonuclease activity has a preference for certain base mismatch combinations (e.g. *C/A) over others (e.g. *T/C). However, these experiments do not rule out an effect on cleavage by the sequence(s) flanking the mismatch.

Uve1p has been shown to incise DNA containing CPDs and 6-4PPs directly 5′ to the photoproduct site generating products containing 3′-hydroxyl and 5′-phosphoryl groups (Bowman et al. [1994] supra). We examined whether similar 3′ and 5′ termini were produced following Uve1p-mediated cleavage of base mismatch-containing substrates. DNA strand scission products generated by GΔ228-Uve1p cleavage of 3′ end-labeled oligo *CX/AY-31mer (CX strand labeled, Table 1B) were further treated with calf intestinal phosphatase (CIP) which removes 5′ terminal phosphoryl groups from substrate DNA. The major sites of Uve1p-mediated DNA cleavage relative to the base mispair site were found to be at positions 0 and −1 (FIG. 11A, lane 2). CIP treatment of these DNA cleavage products resulted in species that had retarded electrophoretic mobilities compared to non-CIP-treated DNA cleavage products, indicating a decrease in charge corresponding to removal of 5′ terminal phosphoryl groups (FIG. 11A, lanes 2 and 3). In addition, GΔ228-Uve1p mismatch endonuclease-generated DNA cleavage products were resistant to phosphorylation by polynucleotide kinase, an expected result if the 5′ termini already contain phosphoryl groups (FIG. 11A, lane 4). Electrophoretic mioibility shift analysis utilizing 5′ end-labeled *CX/AY-31mer, terminal deoxyribonucleotidyl transferase (TdT), and α³²P-dideoxyATP (ddATP) resulted in addition of a single ddAMP to the 3′ end of GΔ228-Uve1p-generated DNA cleavage products and indicates the presence of a 3′-hydroxyl terminus. These results show that the 3′ and 5′ termini of the products of GΔ228-Uve1p-mediated cleavage of substrates containing single base mismatches are identical to those generated following cleavage of substrates containing CPDs or 6-4PPs.

To verify that the Uve1p mismatch endonuclease activity observed was not the result of trace endonucleolytic contamination from the S. cerevisiae expression system and to determine whether full length Uve1p was also capable of mismatch endonuclease activity, extracts from cells overexpressing GFL-Uve1p, GΔ228-Uve1p, and GST tag alone were tested for their abilities to cleave 5′ end-labeled *CX/AY-31mer. Both GFL-Uve1p and GΔ228-Uve1p cleaved the base mismatch-containing substrate at positions 0, −1, and −2 (FIG. 11B). We also observed a weak 3′ to 5′ exonucleolytic activity associated with both crude GFL-Uve1p preparations and purified GΔ228-Uve1p which shortened the Uve1p-mediated cleavage products by one to three nucleotides (FIG. 11B, lanes 1 and 2). These shorter products are not due to additional cleavages by Uve1p mismatch endonuclease activity because they are not observed in identical experiments with 3′ end-labeled substrates. Purified Δ228-Uve1p obtained following thrombin cleavage of the GST tag also possessed mismatch endonuclease activity. In contrast, no cleavage of mismatch-containing substrates was observed when extracts from cells transfected with vector expressing only the GST tag were tested. Thus, both GFL-Uve1p and its more stable, truncated version, GΔ228-Uve1p, both possess mismatch endonuclease activities.

GΔ228-Uve1p mismatch endonuclease and GΔ228-Uve1p UV photoproduct endonuclease share similar properties and compete for the same substrates. GΔ228-Uve1p requires divalent cations for activity and exhibits optimal activity against UV photoproducts in the presence of 10 mM MgCl₂ and 1 mM MnCl₂. Omission of divalent cations from the reaction buffer abolished GΔ228-Uve1p mismatch endonuclease activity on 5′ end-labeled *CS/AY-31mer. The pH optimum for GΔ228-Uve1p mismatch endonuclease activity on this same substrate was found to be 6.5, which corresponds to the pH where optimal activity is observed against UV photoproducts.

To further confirm that the mismatch endonuclease activity was mediated by GΔ228-Uve1p, a substrate competition experiment was performed with CPD-30mer, a known Uve1p substrate which contains a centrally located UV photoproduct (CPD). Addition of increasing amounts of unlabeled CPD-30mer resulted in a significant, concentration-dependent decrease in GΔ228-Uve1p-mediated mismatch endonuclease activity against 3′ end-labeled *CX/AY31mer (C/A mispair) (FIG. 12). In contrast, increasing amounts of the undamaged oligo GX/CY-31mer (G/C base pair) had only a modest inhibitory effect, and inhibition did not increase with increasing amounts of added oligo, indicating a non-specific binding to Uve1p within this concentration range. In a similar experiment both unlabeled CPD-30mer and CX/AY-31mer (C/A mispair) were more potent inhibitors of 3′ end-labeled *CX/AY-3mer cleavage compared to unlabeled GX/CY-31mer. The effective competition by CPD-30mer for mismatch endonuclease activity indicates that both base mismatch and UV photoproduct endonuclease activities are associated with GΔ228-Uve1p.

Uve1p incises only one strand of a duplex containing a base mismatch. Since Uve1p recognizes all possible base mismatch combinations, we determined whether the enzyme could incise both strands on the same molecule resulting in a DNA double strand break. An oligonucleotide (*CX/AY-41mer) was designed such that the base mispair was placed in the center of the oligonucleotide. GΔ228-Uve1p was incubated with 3′ end-labeled *CS/AY-41mer under standard conditions, and the DNA strand scission products were analyzed on both non-denaturing and denaturing gels (FIGS. 13A-13B). In the event that GΔ228-Uve1p created a DNA double strand break by incising 5′ to the base mismatch site on the two complementary strands, the resulting products would possess an electrophoretic mobility similar to those created by the restriction enzyme DdeI (which cleaves adjacent to the mismatch) when analyzed on a non-denaturing polyacrylamide gel. In contrast, if GΔ228-Uve1p incises on either (but not both) complementary strands, then the resulting product would be a full-length duplex containing a single strand nick which would co-migrate with uncut duplex *CX/AY-41mer on a non-denaturing gel. Non-denaturing gel analysis of GΔ228-Uve1p-treated *CX/AY-41mer generated a product with an electrophoretic mobility identical to the untreated duplex with no products detected corresponding to those created by a double strand break (FIG. 13A). Denaturing gel analysis revealed a GΔ228-Uve1p-generated DNA strand scission product resulting from a single strand break of the labeled strand of either *CX/AY-41mer or CX/*GY-41mer. Together with the non-denaturing gel analysis, these results indicate that within the GΔ228-Uve1p substrate population, nicks occur on one or the other, but not both strands (FIG. 13B). These results show that GΔ228-Uve1p nicks only one of the two strands containing a base mismatch and that it does not make double strand breaks in duplex DNA. Similarly, double strand breaks are not made in DNA molecules containing other structural distortions.

Without wishing to be bound by theory, it is believed that GΔ228-Uve1p possesses strand specificity directed towards the 3′ terminus. Mismatched bases in duplex DNA are distinct from damaged DNA in the sense that both of the bases are usually undamaged per se, yet one is an inappropriate change in the nucleotide sequence and must be identified as such and removed. If Uve1p participates in MMR in vivo, how might it distinguish between the correct and incorrect bases in a mispair? One possibility is that proximity of the mispaired base to either the 3′ or 5′ terminus targets Uve1p mismatch endonuclease activity to a particular strand. For example, in DNA synthesis, chain growth proceeds from the 5′ to the 3′ terminus and newly-generated base misincorporations on the synthesized strand would be located in close proximity to the 3′ terminus. Initiating the removal of such bases by a mismatch repair protein might involve association with a region of DNA in the vicinity of the 3′ terminus, followed by targeting of the mispaired base located on that strand. To investigate this possibility, a series of 3′ end-labeled oligonucleotides were generated that contained a C/A mispair located at various distances from the ends (Table 1B). The ability of GΔ228-Uve1p to incise the C-containing strand as a function of the distance of C (of the C/A mispair) from the 3′ terminus was assessed by quantifying the GΔ228-Uve1p mismatch endonuclease-generated DNA stand scission products following denaturing gel analysis. A minimum level of mismatch cleavage was observed for C at a distance of 16 bp from the 3′ terminus and gradually increased to a maximum for C at a distance of 16 bp from the 3′ terminus. Closer placement (11 bp) of C to the 3′ terminus resulted in a decrease in mismatch endonuclease activity with a complete loss of activity observed at a distance 6 bp from the 3′ terminus. The mismatched base located on the strand in closest proximity to the 3′ terminus is cleaved preferentially by GΔ228-Uve1p.

uve1 null mutants exhibit a mutator phenotype. We have examined the spontaneous mutation rate of uve1::ura4⁺ disruption mutants as assayed by the ability to form colonies resistant to the toxic arginine analog L-canavanine. Uptake of L-canavanine in S. pombe is mediated by an arginine permease encoded by the can1⁺ gene (Fantes, P. and Creanor, J. [1984] J. Gen. Microbiol. 130:3265-3273). Mutations in can1⁺ eliminate the uptake of L-canavanine, and mutant cells are able to form colonies on medium supplemented with L-canavanine, whereas wild type cells cannot. We have compared the rate of spontaneous mutagenesis at the can1⁺ locus in uve1::ura4⁺ disruption mutants (Sp362) to both a negative control (wild type, 972) and a positive control, pms1::ura4⁺ (see Example 11 hereinbelow). The pms1 gene product is a homolog of E. coli MutL, and loss of pms1 causes a strong mitotic mutator phenotype and increased postmeiotic segregation (Schar et al. [1997] Genetics 146:1275-1286).

To determine the relative sensitivity of each yeast strain to L-canavanine, 200 cells from mid-log phase cultures were plated onto PMALU^(g) plates supplemented with increasing concentrations of L-canavanine. Each of the strains was equally sensitive to L-canavanine. All strains were viable in the presence of lower concentrations of L-canavanine up to and including concentrations of 2.2 μg/ml, while concentrations higher than this were toxic to all strains. However, the colonies which grew in the presence of 2.2 μg/ml L-canavanine were smaller in diameter than the colonies which grew in the presence of lower concentrations.

The mean spontaneous mutation rate of each of the three strains was examined using fluctuation analyses. Single colonies grown on PMALU^(g) plates were used to inoculate liquid PMALU^(g) cultures which were grown to saturation. 10⁷ cells were plated onto PMALU^(g) containing 75 μg/ml L-canavanine sulfate. The number of colonies on 24 plates for each strain was counted after 8 days incubation at 30° C. Both uve1::ura4⁺ and pms1::ura4⁺ strains showed an elevated number of resistant colonies compared to wild type. Additionally, the range of values for uve1::ura4⁺ was broader and higher than for either wild type or pms1::ura4⁺ and included two confluent plates scored as containing >5000 colonies. the mean rate of mutation was estimated using the method of the median (Lea and Coluson [1943] J. Genet. 49:264-284) using the median values. The calculated mutation rates are 1.5×10⁻⁷ (wild type), 9.7×10⁻⁷ (uve1::ura4⁺), and 2.0×10⁻⁶ (pms1:ura4⁺), indicating that uve1::ura4⁺ mutants have a spontaneous mutation rate approximately 6.5-fold greater than wild type and 2-fold lower than pms1::ura4⁺. See Table 4 for a summary of results. Thus, loss of Uve1p confers a spontaneous mutator phenotype in S. pombe. In the mutation fluctuation analysis, a wide range of mutant colonies was observed for uve1::ura4⁺ compared to uve1::ura4⁺, suggesting that the pathways leading to mutation due to elimination of uve1 and pms1 are likely to be mechanistically different.

The finding that Uve1p recognizes all potential DNA base mispair combinations indicates that, in addition to its UV photoproduct cleavage activity, it is a diverse mismatch endonuclease with broad substrate specificity. In this regard, Uve1p is similar to E. coli endonuclease V (Yao, M. and Kow, Y. W. [1994] J. Biol. Chem. 269:31390-31396), a S. cerevisiae and human “all-type” mismatch endonuclease (Chang, D. Y. and Lu, A. L. [1991] Nucl. Acids Res. 19:4761-4766; Yeh et al. [1991] J. Biol. Chem. 266:6480-6484) and calf thymus topoisomerase I (Yeh et al. [1994] J. Biol. Chem. 269:15498-15504) which also recognize all potential base mismatch combinations. These enzymes incise DNA at each of the twelve base mispairs with variable efficiencies and either to the 5′ (human all-type mismatch endonuclease) or 3′ (E. coli endonuclease V) sides of a mismatch. Uve1p shows a preference for *C/C and *C/A mispairs, a property similar to the human all-type mismatch endonuclease (Yeh et al. [1991] supra). In contrast, the strong preference of Uve1p for *G/G mispairs is a property which distinguishes Uve1p from all other mismatch endonucleases identified to date.

The biochemical properties of Uve1p-mediated mismatch cleavage and the spontaneous mutator phenotype displayed by uve1 null mutants suggest that Uve1p is involved in MMR in vivo. The preference for making incisions on the strand harboring the mispaired base nearest to the 3′ terminus reflects a discrimination strategy that might specifically target newly misincorporated bases during replication. Uve1p-generated incision 5′ to the base mismatch site could be followed by a 5′ to 3′ exonuclease activity such as that mediated by S. pombe exonuclease I (Szankasi, P. and Smith, G. R. [1995] Science 267:1166-1169) or the FEN-1 homolog Rad2p (Alleva, J. L. and Doetsch, P. W. [1998] Nucl. Acids Res. 26:3645-3650) followed by resynthesis and ligation.

S. pombe possesses at least two distinct mismatch repair systems and whether Uve1p mediates a role in either of these or represents a third, novel pathway is not known at present. The proposed major pathway does not recognize C/C mismatches and has relatively long (approximately 100 nt) repair tracts (Schar, P. and Kohli, J. [1993] Genetics 133:825-835). Uve1p is thought to participate in a relatively short patch repair process which utilizes Rad2p (a FEN-1 homolog) DNA polymerase δ, DNA ligase and accessory factors (Alleva et al. [1998] Nucl. Acids Res. 26:3645-3650). Based on these properties, it is unlikely that Uve1p is involved in a long tract mismatch repair system. The second, presumably less frequently utilized, (alternative) pathway recognizes all potential base mismatch combinations and has a repair tract length of about 10 nucleotides (Schar and Kohli [1993] supra). These features of the alternative mismatch repair pathway are consistent with the repair properties of Uve1p based on recognition of C/C mismatches and short repair patch.

Unlike in repair of UV photoproducts, it is not clear in mismatch repair which base represents the nucleotide that needs to be removed. This can be explained by our finding that Uve1p prefers a mispaired base located near the 3′ terminus of a duplex, which is consistent with Uve1p mediating mismatch repair for either leading or lagging strand synthesis during DNA replication. The preference for making incisions on the strand of the base nearest to the 3′ terminus suggests a discrimination strategy to specifically target newly synthesized misincorporated bases. On the other hand, G/G, C/C mismatches are not frequently occurring base misincorporations encountered during replication, although they are among the most efficiently cleaved by Uve1p. A second role for Uve1p is in the correction of mismatched bases formed as a result of homologous recombination events where G/G and C/C mismatches would be expected to occur. A third role for Uve1p is in the repair of base bulges and loops generated as a result of primer-template misalignments during replication. Preliminary studies show that Uve1p mediates strand cleavage 5′ to small bulges.

What is the structural basis for lesion recognition by Uve1p? Previous studies with Uve1p have locused exclusively on its role in the repair of UV light-induced DNA damage, resulting in the notion that this enzyme functions in the repair of UV photoproducts exclusively, hence the prior name UVDE (UV damage endonuclease), now Uve1p. The results of this study clearly indicate a much broader involvement of Uve1p in S. pombe DNA repair and show that many other types of DNA lesions are recognized by this versatile repair protein. For example, we have recently found that Uve1p recognizes and incises DNA substrates containing uracil, dihydrouracil, cisplatin-induced adducts as well as small base bulges. The molecular basis for substrate recognition by Uve1p is not obvious, but without wishing to be bound by theory, it is believed to be due in part to disruption of normal Watson-Crick. base pairing and the corresponding changes expected in the electronic characteristics of the major and minor grooves of B-DNA.

Besides initiating repair of DNA containing UV damage including CPDs and 6-4PPa, UVDE and the truncated UVDE polypeptide of the present invention (A228-UVDE and/or GST-Δ228-UVDE) also initiate repair via cleavage of DNA duplexes containing the following base pair mismatches: C/A; G/A; G/G; A/A; and C/T. These experiments were conducted with GST-Δ228-UVDE. We also confirmed that the C/A mismatch is cleaved by Δ228-UVDE; it should also recognize the others. In addition, both GST-Δ228-UVDE and Δ228-UVDE recognize and cleave an oligonucleotides containing a GG-platinum diadduct formed by the antitumor agent cis-dichlorodiammineplatinum (II) (also known as cisplatin). Thus the substrate specificity range for UVDE is much broader than originally thought. Recognition of the truncated UVDE polypeptide to initiate mismatch repair was made possible due to the increased stability of the presently exemplified truncated UVDE polypeptide in substantially purified form.

Skin cancers associated with sunlight exposure are the most common worldwide human cancers. The primary DNA damage from exposure to sunlight are 6-4 PPs and CPDs. Since UVDE can augment cells defective in DNA repair, the stable truncated UVDE fragments of the present invention will be valuable therapeutic agents for correcting DNA repair defects in sunlight-sensitive and skin cancer-prone individuals, for example individuals with the genetic disease xeroderma pigmentosum. Additionally, GST-Δ228-UVDE and Δ228-UVDE can be used as protective agents against sunlight-induced skin damage in normal individuals because they can augment the existing DNA repair levels of CPDs and 6-4 Pps and other DNA damage.

Homologs of the S. pombe UVDE protein have been identified by BLAST searching of sequence database (Genbank, TIGR) using the UVDE amino acid sequence: N. crassa (Genbank Accession No. BAA 74539), B. subtilis (Genbank Accession No. 249782), human (Genbank Accession No. AF 114784.1, methyl-CpG binding endonuclease) and a Deinococcus radiodurans sequence located from the TIGR database. The amino acid sequences of these proteins are given in SEQ ID NO:36 (N. crassa), SEQ ID NO:37 (B. subtilis), SEQ ID NO:38 (Homo sapiens) and SEQ ID NO:39 (D. radiodurans). The D. radiodurans coding sequence can be generated using the genetic code and codon choice according to the recombinant host in which the protein is to be expressed, or the natural coding sequence can be found on the TIGR database, D. radiodurans genomic sequence in the region between bp 54823 and 60981.

The regions of the S. pombe UVDE protein which are most conserved in the foregoing homologs are amino acids 474-489, 535-553, 578-611, 648-667, 711-737 and 759-775 of SEQ ID NO:2.

The stable truncated UVDE derivatives of the present invention are useful to treat or prevent diseases caused by cyclobutane pyrimidine dimers or (6-4) photoproducts or DNA mismatch, atasic sites or other distortions in the structure of double stranded DNA through the application of skin creams which can deliver GST-Δ228-UVDE and Δ228-UVDE to the appropriate living cells or via other routes of administration with compositions suitable for the route of administration, as is well understood in the pharmaceutical formulation art. GST-Δ228-UVDE or Δ228-UVDE can be incorporated into liposomes, and the liposomes can be applied to the surface of the skin, whereby the encapsulated GST-Δ228-UVDE and Δ228-UVDE products traverse the skin's stratum corneum outer membrane and are delivered into the interior of living skin cells. Liposomes can be prepared using techniques known to those skilled in the art. A preferred liposome is a liposome which is pH sensitive (facilitates uptake into cells). Preparation of pH sensitive liposomes is described in U.S. Pat. No. 5,643,599, issued to Kyung-Dall et al.; and U.S. Pat. No. 4,925,661 issued to Huang. The GST-Δ228-UVDE and Δ228-UVDE polypeptides can be entrapped within the liposomes using any of the procedures well known to those skilled in the art. See, e.g., the Examples and U.S. Pat. No. 4,863,874 issued to Wassef et al.; U.S. Pat. No. 4,921,757 issued to Wheatley et al.; U.S. Pat. No. 5,225,212 issued to Martin et al.; and/or U.S. Pat. No. 5,190,762 issued to Yarosh.

The concentration of liposomes necessary for topical administration can be determined by measuring the biological effect of GST-Δ228-UVDE and Δ228-UVDE, encapsulated in liposomes, on cultured target skin cells. Once inside the skin cell, GST-Δ228-UVDE or Δ228-UVDE repairs CPDs or 6-4 Pps in damaged DNA molecules and increases cell survival of those cells damaged by exposure to ultraviolet light.

Polyclonal or monoclonal antibodies specific to GST-Δ228-UVDE and Δ228-UVDE allow the quantitation of GST-Δ228-UVDE and Δ228-UVDE entrapped into liposomes. GST-Δ228-UVDE and Δ228-UVDE antibodies also allow tracing of the truncated UVDE polypeptides into skin cells.

Standard techniques for cloning, DNA isolation, amplification and purification, for enzymatic reactions involving DNA ligase, DNA polymerase, restriction endonucleases and the like, and various separation techniques are those known and commonly employed by those skilled in the art. A number of standard techniques are described in Sambrook et al. (1989) Molecular Cloning, Second Edition. Cold Spring Harbor Laboratory, Plainview, N.Y.; Maniatis et al. (1982) Molecular Cloning, Cold Spring Harbor Laboratory, Plainview, N.Y.; Wu (ed.) (1993) Meth. Enzymol. Part I; Wu (ed.) (1979) Meth Enzymol. 65; Miller (ed.) (1972) Experiments in Molecular Genetics, Cold Spring Harbor Laboratory, Cold Spring Harbor, N.Y.; Old Primrose (1981) Principles of Gene Manipulation, University of California Press, Berkeley; Schleif and Wensink (1982) Practical Methods in Molecular Biology; Glover (ed.) (1985) Nucleic Acid Hybridization, IRL Press, Oxford, UK; and Setlow and Hollaender (1979) Genetic Engineering: Principles and Methods, Vols. 1-4, Plenum Press, New York. Abbreviations and nomenclature, where employed, are deemed standard in the field and commonly used in professional journals such as those cited herein.

Each reference cited in the present application is incorporated by reference herein to the extent that it is not inconsistent with the present disclosure.

The following examples are provided for illustrative purposes, and are not intended to limit the scope of the invention as claimed herein. Any variations in the exemplified articles which occur to the skilled artisan are intended to fall within the scope of the present invention.

EXAMPLES Example 1 Strains, Enzymes, Plasmids and Genes

E. coli Top10 (Invitrogen Corp., San Diego, Calif.) was used for subdloning and plasmid propagation. S. cerevisiae strain DY150 used for protein expression and the S. cerevisiae expression vector pYEX4T-1 were purchased from Clontech (Palo Alto, Calif.).

S. pombe strains used in this study include 972, h^(−s) (Leupold, U. [1970] Meth. Cell Physiol. 4:169-177); PRS301, h^(−s) pms1::ura4⁺ (Schar et al. [1993] Genetics 146:1275-1286); SP30, h^(−s) ade6-210 leu-32 ura4-D18 (Davey et al. [1998] Mol. Cell. Biol. 18:2721-2728). Sp362 (h^(−s) ade6-210 leu1-32 ura4-D18 uve1::ura4⁺) was constructed by transforming Sp30 with a linearized, genomic uve1⁺fragment derived from pgUV2 (Davey et al. [1997] Nucl. Acids Res. 25:1005-1008) in which nucleotides 215 (EcoRI) to 1045 (ClaI) of uve1⁺ were replaced with the ura4⁺ gene. Extracts of Sp362 contained no detectable Uve1p activity against CPD-30mer. Cultures were grown in pombe minimal medium (PM) (Leupold [1970 supra) with 3.75 g/l glutamate replacing ammonium chloride as the nitrogen source (Fantes, P. and Creanor, J. [1984] J. Gen. Microbiol. 130:3265-3273), and were supplemented with 150 mg/l of each adenine, leucine and uracil (PMALU^(g)). Solid media was prepared by addition of 20 g/l agar. L-canavanine sulfate was sterilized prior to addition to the medium.

Purified mismatch repair endonuclease, E. coli endonuclease V (Yao, M. and Kow, Y. W. [1997] J. Biol. Chem. 272:30774-30779) was a gift from Yoke Wah Kow (Atlanta, Ga.).

Example 2 Amplification of the uvde (uve1) Gene from S. pombe

A cDNA library purchased from ATCC was amplified by PCR, using the sense primer: 5′-TGAGGATCCAATCGTTTTCATTTTTTAATGCTTAGG-3′ (SEQ ID NO:9) and the antisense primer: 5′-GGCCATGGTTATTTTTCATCCTC-3′ (SEQ ID NO:10). The gene fragment of interest was amplified in the following manner. Four hundred nanograms of template DNA (S. pombe cDNA library) was incubated with the upstream and downstream primers (300nM) in the presence of Pwo DNA polymerase (Boehringer Mannheim, Indianapolis, Ind.) in 10 mM Tris-HCl (pH 8.85), 25 mM KCl, 5 mM (NH₄)₂SO₄, 2 mM MgSO₄ and 200 μM of dNTPs. The DNA was initially denatured at 94° C. for 2 min. Three cycles of denaturation at 94° C. for 15 sec, annealing at 45° C. for 30 sec and primer extension at 72° C. for 2 min were followed by twenty cycles using 50° C. as the annealing temperature. All other incubation times and temperatures remained the same. The amplification was completed by a final primer extension at 72° C. for 7 min.

Example 3 Amplification of the Δ228-UVDE Gene-encoding Fragment from S. pombe

PCR was used to produce a truncated DNA fragment of the full-length S. pombe uvde gene which encodes a protein product containing a deletion of 228aa from the N-terminal portion of the full-length S. pombe UVDE protein. The following primers were used in the PCR reaction to amplify the gene fragment which encodes Δ228-UVDE: sense primer 5′-AATGGGATCCGATGATCATGCTCCACGA-3′ (SEQ ID NO:11) and the antisense primer 5′-GGGATCCTTATTTTTCATCCTCTTCTAC-3′ (SEQ ID NO:12). PCR conditions were as described in Example 2.

Example 4 Purification of Δ228-UVDE and Full-length UVDE

The amplified UVDE gene coding fragments were cloned into the BamHI and SmaI restriction sites of pYEX 4T-1. The Δ228-UVDE gene coding fragments were cloned into the BamHI restriction site of pYEX4T-1 (Clontech, Palo Alto, Calif.). In the pYEX4T-1 vector, the coding region of both the proteins is expressed in frame with a glutathione-S-transferase (GST) leader sequence to generate a fusion protein of GST linked to the N-terminus of UVDE which is under the control of the CUP1 promoter (Ward et al., 1994). The subcloned plasmids were checked for orientation by restriction analysis and were then transformed into S. cerevisiae, DY150 cells, using the alkali cation method (Ito et al. [1983] supra). A single positive clone was picked and grown at 30° C. until mid log phase. Cultures in mid log phase were induced with 0.5 mM CuSO₄. Cells (500 mL) were harvested 2 hr after induction and lysed with glass beads in 50 mM Tris (pH 7.5), 100 mM EDTA, 50 mM NaCl, 10 mM β-mercaptoethanol, 5% glycerol in the presence of 10 ng/mL pepstatin, 3 nN leupeptin, 14.5 mM benzamidine, and 0.4 mg/mL aprotinin. The cell lysate was then dialyzed overnight in buffer minus EDTA. The whole cell homogenate was separated into soluble and insoluble fractions by centrifugation at 45,000× g for 20 min. The soluble proteins (120 mg) were applied to a 2 mL glutathione-Sepharose-affinity column (Pharmacia, Piscataway, N.J.). All purification steps were carried out at 4° C. and are similar to the strategies employed for the purification of other types of GST-tagged proteins (Ward, A. C. et al. [1994] Yeast 10:441-449; Harper, S. and Speicher, D. [1997] in Current Protocols in Protein Sci. [Coligan, J. et al., Eds) pp. 6.6.1-6.6.21, John and Wiley & Sons). Unbound proteins were removed by washing with 30 mL phosphate-buffered saline (pH 7.4), 5 mM EDTA, 0.15 mM PMSF. GST-Δ228-UVDE was eluted (100-200 μL fractions) with 10 mM glutathione in 50 mM Tris (pH 7.4) or cleaved on the column with excess of thrombin as previously described (Harper and Speicher, 1997) to generate Δ228-UVDE without the GST tag. SDS-PAGE analysis of flow-through, wash, elution, and thrombin cleavage fractions indicated the extent of purification or GST tag removal via thrombin cleavage (FIGS. 1A-1B).

Example 5 GST Preparation

S. ceievisiae (DY150) cells were transformed with the pYex4T-1 expression vector without any insert (i.e., expressing gluthathione-S-transferase [GST] alone). These cultures were induced with CuSO₄ and cell lysates were prepared as described for the Uve1p proteins. Purified recombinant GST was affinity-purified on a gluthathione sepharose column in an identical manner to GΔ228-Uve1p (see above) and was included in all of the assays performed in this study as a control for trace amounts of potential contaminating endonucleases in the Uve1p protein preparations.

Example 6 UVDE Activity Assay and Optimization of Reaction Conditions

Crude and purified full-length UVDE, GST-Δ228-UVDE and Δ228-UVDE were tested for activity on an oligodeoxynucleotide substrate (CPD-30mer) containing a single cis-syn cyclobutane pyrimidine dimer embedded near the center of the sequence. The sequence of the CPD-containing strand is: 5′-CATGCCTGCACGAATATAAGCAATTCGTAAT-3′ (SEQ ID NO:13). The CPD-containing DNA molecule was synthesized as described by Smith, C. A. and Taylor, J. S. (1993) J. Biol. Chem. 268:11143-11151. The CPD-30mer was 5′ end labeled with [γ-³²P]ATP (Amersham, 3000 Ci/mmol) using polynucleotide kinase (Tabor, 1989). For UVDE reactions with end labeled CPD-30mer, approximately 10 fmol of 5′ end labeled CPD 30-mer was incubated with 5-100 ng of Δ228-UVDE or GST-Δ228-UVDE, in 200 mM Hepes (pH 6.5), 10 mM MgCl₂, 1 mM MnCl₂, 150 mM NaCl for 15 min at 37° C. 10-20 μL reaction volume). The reaction products were analyzed on 20% denaturing (7 M urea) polyacrylamide gels (DNA sequencing gels) as previously described (Doetsch, et al., 1985). The DNA spec(ies corresponding to the uncleaved CPD-30mer and cleavage product (14-mer) were analyzed and quantified by phosphorimager analysis (Molecular Dynamics Model 445SI) and autoradiography.

In other experiments, reactions with various Uve1p preparations were carried out in a total volume 20 μL, and contained reaction buffer (20 mM Hepes, pH 6.5, 100 mM NaCl, 10 mM MgCl₂ and 1 mM MnCl₂) and end-labeled oligonucleotide substrate (10-30 fmol). The substrate/buffer mix was incubated for 20 min at 37° C. with Uve1p. In the case of G-Uve1p and GΔ228-Uve1p, crude cell lysates (5 μg of protein) were used for all assays. Fifty ng of affinity-purified GΔ228-Uve1p (0.75 pmol) and Δ228-Uve1p (1.2 pmol) were incubated with all of the UV-induced photoproducts. For all other assays 2 μg of affinity-purified GΔ228-Uve1p (30 pmol) and Δ228-Uve1p (48 pmol) were incubated with the substrates. Two μg of affinity-purified recombinant GST (72 pmol) was incubated with each substrate under Δ228-Uve1p optimum reaction conditions to control for potential contaminating nuclease activities which may be present in the Uve1p preparations and to determine the specificity of the Uve1p cleavage reaction. DNA repair proteins (E. coli exonuclease III, E. coli endonucleases III and IV, E. coli uracil DNA glycosylase and S. cerevisiae enclonuclease III-like glycosylase [Ntg]) specific for each oligonucleotide substrate were also incubated with these substrates under their individual optimum reaction conditions, as a means to determine the specific DNA cleavage sites of Uve1p. The reaction products were analyzed on 20% denaturing (7M urea) polyacrylamide gels (DNA sequencing-type gels) as described previously (Doetsch et al. [1985] Nucl. Acids Res. 13:3285-3304). The DNA bands corresponding to the cleaved and uncleaved substrate were analyzed and quantified by phosphorimager analysis (Molecular Dynamics Model 445SI) and autoradiography.

Example 7 Oligonucleotides Containing DNA Damage

The DNA damage-containing oligonucleotides used as substrates in this study are presented in Table 1A. The structure of each damaged lesion is presented in FIG. 1. The 30-mer cs-CPD-containing oligonucleotide (cs-CPD-30mer) was prepared as described previously (Smith, C. A. [1993] J. Biol Chem. 268:11143-11151). The 49-mer oligonucleotides containing a cs-CPD (cs-CPD-49mer), a ts I-CPD (tsI-CPD-49mer), a ts II-CPD (tsII-CPD-49mer), a 6-4PP (6-4PP-49mer) and a Dewar isomer (Dewar-49mer) were synthesized as described previously (Smith, C. A. and Taylor, J-S. [1993] J. Biol. Chem. 268:11143-11151). The oligonucleotide containing a platinum-DNA GG diadduct (Pt-GG-32mer) and its complementary strand were prepared as previously described (Naser et al. [1988] Biochemistry 27:4357-4367). The uracil-containing oligonucleotide (U-37mer), the undamaged oligonucleotides and the complementary strand oligonucleotides for all the substrates were synthesized by the Emory University Microchemical Facility. The DHU-containing oligonucleotide (DHU-37mer) was synthesized by Research Genetics (Birmingham, Ala.). The oligonucleotides containing inosine (I-31mer) and xanthine (Xn-31mer) and their complementary strands were a gift from Dr. Yoke Wah Kow (Emory University, Atlanta, Ga.). The 8-oxoguanine-containing 37-mer (8-oxoG-37mer) was synthesized by National Biosciences Inc. (Plymouth, Minn.).

Labelied oligonucleotide substrates were prepared as follows: The cs-CPD-30mer, the 49mer UV photodamage-containing oligonucleotides and the Pt-GG-32mer were 5′ end-labeled with [γ-³²P] ATP (Amersham, 3000 Ci/mmol) using polynucleotide kinase (Tabor, S. [1985] in Current Protocols in Molecular Biology, Greene Publishing Associates and Wiley [Interscience], New York, N.Y.). the oligonucleotides U-37mer, DHU-37mer, 1-31mer, Xn-31mer and 8-oxoG-37mer were 3′ end-labeled using terminal transferase and [α³²P] ddATP (Amersham, 3000 Ci/mmol) (Tu, C. and Cohen, S. N. [1980] Gene 10:177-183). End-labeled duplex oligonucleotides were gel-purified on a 20% non-denaturing polyacrylamide gel. The DNA was resuspended in ddH₂O and stored at −20 C.

The AP substrate was prepared as described hereinbelow. 5′ end-labeled, duplex U-37mer (20-50 pmol) was incubated with uracil DNA glycosylase (UDG, 6 units) for 30 minutes at 37° C. in UDG buffer (30 mM Hepes-KOH, pH 7.5, 1 mM EDTA, and 50 mM NaCl) to generate the AP site-containing oligonucleotide (AP-37mer). The DNA was extracted with PCIA (phenol-chloroform-isoamylalcohol, 29:19:1, v/v/v) equilibrated with HE buffer (10 mM Hepes-KOH pH 8.0, 2 mM EDTA) with 0.1% 8-hydroxyquinoline, and was evaluated for its AP site content by cleavage with 0.1 M piperidine at 90° C. for 20 minutes.

The CPD-30mer Uve1p substrate (see herein and Kaur et al. [1998] Biochemistry 37:11599-11604) containing a centrally embedded, cis-syn TT cyclobutane pyrimidine dimer was a gift from John-Stephen Taylor (St. Louis, Mo.). All other oligonucleotide substrates (Table 1) for mismatch endonuclease experiments were synthesized by Operon, Inc. (Alameda, Calif.) or IDT, Inc. (Coralville, Iowa). All oligonucleotides were gel-purified and subjected to DNA sequence analysis for sequence confirmation. Oligonucleotides were 5′ end-labeled with polynucleotide kinase using 50 μCi [γ-³²P] ATP (Amersham, 3000 Ci/mmol) as previously described (Bowman et al. [1994] Nucl. Acids Res. 22:3026-3032). 3′ end-labeled oligonucleotides were prepared by incubating 10 pmol of the indicated oligonucleotide with 10 units of terminal deoxynucleotidyl transferase (TdT, Promega) and 50 μCI of [α-³²P] ddATP (Amersham, 3000 Ci/mmol) as previously described (Bowman et al. [1994] supra).

Example 8 Establishment of Optimal Reaction Conditions

The optimal reaction conditions for UVDE cleavage of CPD-30mer were established by varying the NaCl concentration, divalent cation (MnCl₂, and MgCl₂) concentration, or by varying the pH of the reaction buffer in the reaction. The buffers (20 mM at the indicated pH range) were as follows: sodium citrate (pH 3-6), Hepes-KOH (pH 6.5-8), and sodium carbonate (pH 9-10.6). The optimum temperature required for enzyme activity was determined by pre-incubating the enzyme and the substrate in the reaction buffer at a specific temperature for 10 min prior to mixing UVDE and CPD-30mer. The reaction was stopped by phenol-chloroform-isoamyl alcohol extraction and the reaction products were analyzed on DNA sequencing gels as described above. From these experiments the following standard reaction conditions were established: 20 mM Hepes (pH 7.5), 100 mM NaCl, 10 mM MgCl₂, 1 mM MnCl₂, 30° C. or at 37° C. for 20 minutes.

Example 9 Kinetic Assays

Enzyme reactions were carried out with 5 nM Δ228-UVDE or 11.5 nM GST-Δ228-UVDE in 20 mM Hepes (pH 6.5) in 10 mM MgCl₂, 1 mM MnCl₂, 100 mM NaCl. 5′ End labeled CPD-30mer concentrations were varied from 25-250 nM in a final reaction volume of 15 μL for 0-3 minutes at 37° C. Initial enzyme velocities (V_(i)) were measured for each substrate concentration as nM of product formed per second. The apparent K_(m), V_(max), and turnover number (K_(cat)) were determined from Lineweaver Burk plots of averaged data (±standard deviations) from three independent experiments.

Example 10 Analysis of Uve1P Mismatch Repair Activity

Reactions with GΔ228-Uve1p were carried out by incubating approximately 100 fmol of labeled oligonucleotide substrate with 100-150 ng of purified GΔ228-Uve1p in 20 mM Hepes (pH 6.5), 10 mM MgCl₂, 1 mM MnCl₂, and 150 mM NaCl for 20 minutes at 37° C. (10-20 μl final volume). Reactions with crude preparations of GFL-Uve1p were carried out with 20-30 μg of cell extract incubated with the appropriate substrate in 20 mM Hepes (pH 7.5), 100 mM NaCl, 10 mM MgCl₂ and 1 mM MnCl₂ at 37° C. for 20 minutes. The reaction products were processed by extracting with an equal volume of phenol-chloroform-isoamyl alcohol (25:24:1), ethanol-precipitation, resuspension and analysis on 20% denaturing (7 M urea) polyacrylamide (DNA sequencing) gels as previously described (Kaur et al. [1998] supra). The DNA species corresponding to the uncleaved substrate and Uve1p-mediated DNA strand scission products were analyzed and quantified by phosphorimager analysis (Molecular Dynamics model 445SI) and autoradiography.

Terminal analysis of the mismatch cleavage products was carried out as follows. GΔ228-Uve1p was incubated with 3′ end-labeled *CX/AY-31mer under standard reaction conditions at 37° C. for 20 minutes. The ethanol-precipitated reaction products were incubated with either 10 units of calf intestinal phosphatase (CIP, Promega, Madison Wisc.) at 37° C. for 30 minutes or with 10 units of T4 polynucleotide kinase (PNK, New England Biolabs) and 50 pmol ATP as previously described (Bowman et al. [1994] supra). The reaction products were analyzed on 20% denaturing polyacrylamide gels as described above for Uve1p activity assays. Differences in electrophoretic mobilities of kinase-treated versus untreated DNA strand scission products indicated the presence or absence of a pre-existing 5′-phosphoryl group (Bowman et al. [1994] supra).

3′ terminal analysis of the mismatch cleavage products was carried out as follows. To determine the chemical nature of the 3′ terminus of GSTΔ228-Uve1p-mediated DNA strand scission products, 5′ end-labeled *CX/AY-31mer was incubated with GΔ228-Uve1p as described above. The ethanol-precipitated, resuspended reaction products were then treated with 10 units of TdT and ddATP as previously described (Bowman et al [1994] supra). Samples were processed and analyzed on polyacrylamide gels as described above for 5′ terminal analysis.

To determine the pH optimum for Uve1p-mediated mismatch cleavage, 100 fmol of 3′ end-labeled *CX/AY-31mer was incubated with approximately 100 ng of GΔ228-Uve1p with 10 mM MgCl₂ and 1 mM MnCl₂ in 20 mM reaction buffer of different pH ranges (pH 3.0-10.6). The buffers were as follows: sodium citrate (pH 3.0-6.0), Hepes-KOH (pH 6.5-8.0), and sodium carbonate (pH 9.0-10.6). The reaction products were analyzed on a 20% denaturing polyacrylamide gel and the optimal pH was calculated as previously described for Uve1p cleavage of CPD-30mer (Kaur et al. [1998] supra).

For substrate competition assays, end-labeled *CX/AY-31mer was generated by annealing 3′ end-labeled CX with unlabeled strand AY. Unlabeled non-specific (non-mismatch) competitor GX/CY-31mer was made by annealing strand GX to strand CY resulting in a duplex oligonucleotide with a C/A base pair instead of a G/G mispair. CPD-30mer, a well-characterized substrate for Uve1p, was employed as an unlabeled, specific competitor. 3′ end-labeled *CX/AY-31mer (0.1 pmol) was incubated with 100 ng of purified GΔ228-Uve1p and increasing amounts (0.1-2.0 pmol) of either specific (CPD-30mer) or non-specific (GX/CY-31mer) competitor. The competition reactions were processed and analyzed on 20% denaturing gels as described above. The DNA species corresponding to the uncleaved *GX/GY-31mer and the DNA strand scission products were quantified by phosphorimager analysis (Molecular Dynamics model 445SI).

Example 11 Mutation Frequencies Assayed By Canavanine Resistance

To determine sensitivity to L-canavanine, 10 ml of PMALU^(g) was inoculated with 100 μl of the indicated saturated culture and grown to mid-log phase at 25° C. 200 cells were plated onto PMALU^(g) plates with varying concentrations of L-canavanine sulfate (0, 0.075, 0.22, 0.75, 2.2, 7.5, 22, and 75 μg/ml) and incubated at 30° C. Colonies were counted after four days and viability was normalized against the 0 g/ml plate for each strain. Colony formation assays were conducted for each strain by plating 10⁷ cells from saturated cultures onto PMALU^(g) plates supplemented with 75 μg/ml L-canavanine sulfate. Colonies were counted after eight days incubation at 30° C. Mean mutation frequencies were calculated using the method of the median as described by Lea and Coulson (1943) J. Genet. 49:264-284.

TABLE 1A Damaged Oligonucleotide Substrates Used in This Study. cis-syn cyclobutane pyrimidine dimers (cs-CPDs), trans-syn I CPD (tsI-CPD), trans-syn II CPD (tsII-CPD), (6-4) photoproducts (6-4PP), a Dewar isomer (Dewar), a platinum DNA diadduct (Pt-GG), uracil (U), dihydrouracil (DHU), abasic site (AP), inosine (I), xanthine (Xn) and 8-oxoguanine (8-oxoG). ^(a)Opposite SEQ ID Substrate Damaged oligonucleotide sequence 5′ to 3′ Adduct base(s). NO.: A: cs-CPD-30mer CATGCCTGCACGAAT{circumflex over ( )}TAAGCAATTCGTAAT cs-CPD AA 13 B: UD-30mer CATGCCTGCACGAATTAAGCAATTCGTAAT undamaged AA 14 C: cs-CPD-49mer AGCTACCATGCCTGCACGAAT{circumflex over ( )}TAAGCAATTCGTAATCATGGTCATAGCT cs-CPD AA 15 D: tsI-CPD-49mer ″ tsI-CPD AA 16 E: tsII-CPD-49mer ″ tsII-CPD AA 17 F: 6-4PP-49mer ″ 6-4PP AA 18 G: Dewar-49mer ″ Dewar AA 19 H: Pt-GG-32mer TCCCTCCTTCCTTCCG*G*CCCTCCTTCCCCTTC Pt-GG CC 20 I: U-37mer CTTGGACTGGATGTCGGCACXAGCGGATACAGGAGCA U A/G 21 J: DHU-37mer ″ DHU A/G 22 K: AP-37mer ″ AP A/G 23 L: I-31mer TGCAGGTCGACTXAGGAGGATCCCCGGGTAC I T/C 24 M: Xn-31mer ″ Xn T/C 25 N: 8-oxoG-37mer CTTGGACTGGATGTCGGCACXAGCGGATACAGGAGCA 8-oxoG A/T/G/C 26 ^(a)denotes the bases that are placed opposite to the lesions on the complementary DNA strand. {circumflex over ( )}, *, X represent a UV induced dimer between two adjacent thymines, a cisplatin induced diadduct between two adjacent guanines and position at which the adducts U, DHU, AP, I, Xn and 8-oxoG are incorporated into the oligonucleotide substrates, respectively.

TABLE 1B Base Mismatch and CPD-Containing Oligonucleotides Used in This Study. Oligo Name Sequence Strand Designation SEQ ID NO: XY-31mer¹ 5′ GTACCCGGGGATCCTCCXAGTCGACCTGCA 3′ GX, AX, TX, CX: X = G, A, T, C 27 3′ CATGGGCCCCTAGGAGGYTCAGCTGGACGT 5′ GY, AY, TY, CY: Y = G, A, T, C CX/AY-41mer 5′ CGTTAGCATGCCTGCACGAACTAAGCAATTCGTAATGCATT 3′ CX 28 3′ GCAATCGTACGGACGTGCTTAATTCGTTAAGCATTACGTAA 5′ AY C(6)/A-41mer² 5′ CGTTACAAGTCCGTCACGAATTAAGCAATTCGTAACGCATT 3′ C(6)  29 3′ GCAATGTTCAGGCAGTGCTTAATTCGTTAAGCATTACGTAA 5′ A(36) C(11)/A-41mer 5′ CGTTACAAGTCCGTCACGAATTAAGCAATTCGTAACGCATT 3′ C(11) 30 3′ GCAATGTTCAGGCAGTGCTTAATTCGTTAAACATTGCGTAA 5′ A(31) C(16)/A-41mer 5′ CGTTACAAGTCCGTCACGAATTAAGCAATTCGTAACGCATT 3′ C(16) 31 3′ GCAATGTTCAGGCAGTGCTTAATTCATTAAGCATTGCGTAA 5′ A(26) C(22)/A-41mer 5′ CGTTACAAGTCCGTCACGACTTAAGCAATTCGTAACGCATT 3′ C(22) 32 3′ GCAATGTTCAGGCAGTGCTAAATTCGTTAAGCATTGCGTAA 5′ A(20) C(27)/A-41mer 5′ CGTTACAAGTCCGTCACGAATTAAGCAATTCGTAACGCATT 3′ C(27) 33 3′ GCAATGTTCAGGCAATGCTTAATTCGTTAAGCATTGCGTAA 5′ A(15) C(32)/A-41mer 5′ CGTTACAAGCCCGTCACGAATTAAGCAATTCGTAACGCATT 3′ C(32) 34 3′ GCAATGTTCAGGCAGTGCTTAATTCGTTAAGCATTGCGTAA 5′ A(10) C(37)/A-41mer 5′ CGTTCCAAGTCCGTCACGAATTAAGCAATTCGTAACGCATT 3′ C(37) 35 3′ GCAAAGTTCAGGCAGTGCTTAATTCGTTAAGCATTGCGTAA 5′ A(5)  CPD-30mer³ 5′ CATGCCTGCACGAAT{circumflex over ( )}TAAGCAATTCGTAAT 3′ 30 D 13 3′ GTACGGACGTGCTTA ATTCGTTAAGCATTA 5′ 30 C ¹Series of 16 different duplex oligos containing all possible base pair/mispair combinations between G, A, T, and C. In text, * denotes labeled strand (e.g. *CX/AY-31mer corresponds to C/A mismatch with the C-containing X strand as the labeled strand). ²C/A mismatch oligos designated by base position of the mismatched C from the 3″ terminus. ³CPD-30mer contains a cyclobutane pyrimidine dimer designated as T{circumflex over ( )}T.

TABLE 2 Activity of Uvelp on Oligonucleotide Substrates Containing Uracil, Dihydrouracil and AP sites Protein U/G U/A DHU/G DHU/A AP/G AP/A ^(a)Positive 90-100 50-60 70-80 15-20 90-100 90-100 control GΔ228-Uvelp 8-12 1-5 37-42 10-15 90-100 90-100 GST 1-5  1-5 1-5 1-5 1-5  1-5  The percent of substrate converted into total DNA cleavage products formed when the DNA damage lesion is base paired with a G or an A in the complementary strand. Details of experiments are outlined in Example 10. ^(a)Positive control: when analyzing U 37mer, uracil DNA glycosylase (UDG) was used as a positive control; for assays involving DHU 37mer, the S. cerevisiae endonuclease III-like homolog Ntg1 was used as a positive control; E. coli endonuclease IV was used as a positive control for AP endonuclease activity.

TABLE 3 Uvelp Cleavage Efficiency on Different Substrates. Substrate Percent Cleavage^(a) cs-CPD 49mer 89 tsI-CPD 49mer 75 tsII-CPD 49mer 75 6-4PP 49mer 71 Dewar 83 AP 37mer 12.5 DHU 37mer 3 Pt-GG 32mer 2.5 U 37mer 1 8-oxoG 37mer 0 I 31mer 0 Xn 31mer 0 ^(a)The percent cleavage was calculated by quantifying the amount of Uvelp-mediated cleavage product formed when 300 ng of affinity-purified GΔ228-Uvelp was incubated with ˜150 fmol of each substrate.

TABLE 4 Spontaneous Mutation Rates of uve1 and pms1 Null Mutants Distribution of canavanine- resistant colonies/plate Median no. of Calculated mutation Genotype 0-2 3-34 35-86 >86 colonies/10⁷ cells frequency (mean ± SE) Wild type 18  16 2  0 2.5 1.5 × 10⁻⁷ ± 2.5 × 10⁻⁸ uve1::ura4⁺ 4 14 8 10 34.5 9.7 × 10⁻⁷ ± 4.2 × 10⁻⁸ pms1::ura4⁺ 0  8 10  18 86.5 2.0 × 10⁻⁶ ± 5.0 × 10⁻⁸

TABLE 5 Nucleotide Encoding GST-Full-length UVDE (SEQ ID NO:1) 1 atgaccaagt tacctatact aggttattgg aaaaattaag ggccttgtgc 51 aacccactcg acttcttttg gaatatcttg aagaaaaata tgaagagcat 101 ttgtatgagc gcgatgaagg tgataaatgg cgaaacaaaa agtttgaatt 151 gggtttggag tttcccaatc ttccttatta tattgatggt gatgttaaat 201 taacacagtc tatggccatc atacgttata tagctgacaa gcacaacatg 251 ttggttggtt gtccaaaaga gcgtgcagag atttcaatgc ttgaaggagc 301 ggttttggat attagatacg gtgtttcgag aattgcatat agtaaagact 351 ttgaaactct caaagttgat tttcttagca agctacctga aatgctgaaa 401 atgttcgaag atcgtttatg tcataaaaca tatttaaatg ttgaccatgt 451 aacccatcct gacttcatgt tgtatgacgc tcttgatgtt gttttataca 501 tggacccaat gtgcctggat gcgttcccaa aattagtttg ttttaaaaaa 551 cgtattgaag ctatcccaca aattgataag tacttgaaat ccagcaagta 601 tatagcatgg cctttgcagg gctggcaagc cacgtttggt ggtggcgacc 651 atcctccaaa atcggatcat ctggttccgc gtggatccat gcttaggcta 701 ttgaaacgaa atattcaaat ctctaaacgc attgttttca ccatattaaa 751 acaaaaggca tttaaaggta atcatccttg tgtaccgtcg gtttgtacca 801 ttacttactc tcgttttcat tgtttacccg atacccttaa aagtttactt 851 ccaatgagct caaaaaccac actctcaatg ttaccgcaag ttaatatcgg 901 tgcgaattca ttctctgccg aaacaccagt cgacttaaaa aaagaaaatg 951 agactgagtt agctaatatc agtggacctc acaaaaaaag tacttctacg 1001 tctacacgaa agagggcacg tagcagtaaa aagaaagcga cagattctgt 1051 ttccgataaa attgatgagt ctgttgcgtc ctatgattct tcaactcatc 1101 ttaggcgatc gtcgagatca aaaaaaccgg tcaactacaa ttcctcgtca 1151 gaatccgaat cggaggagca aattagtaaa gctactaaaa aagttaaaca 1201 aaaagaggaa gaggagtatg ttgaagaagt cgacgaaaag tctcttaaaa 1251 atgaaagtag ctctgacgag ttcgaaccgg ttgtgccgga acagttggaa 1301 actccaattt ctaaacgaag acggtctcgt tcttctgcaa aaaatttaga 1351 aaaagaatct acaatgaatc ttgatgatca tgctccacga gagatgtttg 1401 attgtttgga caaacccata ccctggcgag gacgattggg gtatgcttgt 1451 ttgaatacta ttttaaggtc aatgaaggag agggtttttt gttcacgcac 1501 ctgccgaatt acaaccattc aacgtgatgg gctcgaaagt gtcaagcagc 1551 taggtacgca aaatgtttta gatttaatca aattggttga gtggaatcac 1601 aactttggca ttcacttcat gagagtgagt tctgatttat ttcctttcgc 1651 aagccatgca aagtatggat atacccttga atttgcacaa tctcatctcg 1701 aggaggtggg caagctggca aataaatata atcatcgatt gactatgcat 1751 cctggtcagt acacccagat agcctctcca cgagaagtcg tagttgattc 1801 ggcaatacgt gatttggctt atcatgatga aattctcagt cgtatgaagt 1851 tgaatgaaca attaaataaa gacgctgttt taattattca ccttggtggt 1901 acctttgaag gaaaaaaaga aacattggat aggtttcgta aaaattatca 1951 acgcttgtct gattcggtta aagctcgttt agttttagaa aacgatgatg 2001 tttcttggtc agttcaagat ttattacctt tatgccaaga acttaatatt 2051 cctctagttt tggattggca tcatcacaac atagtgccag gaacgcttcg 2101 tgaaggaagt ttagatttaa tgccattaat cccaactatt cgagaaacct 2151 ggacaagaaa gggaattaca cagaagcaac attactcaga atcggctgat 2201 ccaacggcga tttctgggat gaaacgacgt gctcactctg atagggtgtt 2251 tgactttcca ccgtgtgatc ctacaatgga tctaatgata gaagctaagg 2301 aaaaggaaca ggctgtattt gaattgtgta gacgttatga gttacaaaat 2351 ccaccatgtc ctcttgaaat tatggggcct gaatacgatc aaactcgaga 2401 tggatattat ccgcccggag ctgaaaagcg tttaactgca agaaaaaggc 2451 gtagtagaaa agaagaagta gaagaggatg aaaaataaaa at

TABLE 6 Deduced Amino Acid Sequences of GST-Full-Length UVDE (SEQ ID NO:2) 1 mtklpilgyw kikglvqptr llleyleeky eehlyerdeg dkwrnkkfel 51 glefpnlpyy idgdvkltqs maiiryiadk hnmlggcpke raeismlega 101 vldirygvsr iayskdfetl kvdflsklpe mlkmfedrlc hktylngdhv 151 thpdfmlyda ldvvlymdpm cldafpklvc fkkrieaipq idkylkssky 201 iawplqgwqa tfgggdhppk sdhlvprgsm lrllkrniqi skrivftilk 251 qkafkgnhpc vpsvctitys rfhclpdtlk sllpmssktt lsmlpqvnig 301 ansfsaetpv dlkkenetel anisgphkks tststrkrar sskkkatdsv 351 sdkidesvas ydssthlrrs srskkpvnyn ssseseseeq iskatkkvkq 401 keeeeyveev dekslkness sdefepvvpe qletpiskrr rsrssaknle 451 kestmnlddh apremfdcld kpipwrgrlg yaclntilrs mkervfcsrt 501 crittiqrdg lesvkqlgtq nvldliklve wnhnfgihfm rvssdlfpfa 551 shakygytle faqshleevq klankynhrl tmhpgqytqi asprevvvds 601 airdlayhde ilsrmklneq lnkdavliih lggtfegkke tldrfrknyq 651 rlsdsvkarl vlenddvsws vqdllplcqe lniplvldwh hhnivpgtlr 701 egsldlmpli ptiretwtrk gitqkqhyse sadptaisgm krrahsdrvf 751 dfppcdptmd lmieakekeq avfelcrrye lgnppcplei mgpeydqtrd 801 gyyppgaekr ltarkrrsrk eeveedek

TABLE 7 Nucleotide Sequence Encoding Δ228-UVDE (SEQ ID NO:3) 1 gatgatcatg ctccacgaga gatgtttgat tgtttggaca aacccatacc 51 ctggcgagga cgattggggt atgcttgttt gaatactatt ttaaggtcaa 101 tgaaggagag ggttttttgt tcacgcacct gccgaattac aaccattcaa 151 cgtgatgggc tcgaaagtgt caagcagcta ggtacgcaaa atgttttaga 201 tttaatcaaa ttggttgagt ggaatcacaa ctttggcatt cacttcatga 251 gagtgagttc tgatttattt cctttcgcaa gccatgcaaa gtatggatat 301 acccttgaat ttgcacaatc tcatctcgag gaggtgggca agctggcaaa 351 taaatataat catcgattga ctatgcatcc tggtcagtac acccagatag 401 cctctccacg agaagtcgta gttgattcgg caatacgtga tttggcttat 451 catgatgaaa ttctcagtcg tatgaagttg aatgaacaat taaataaaga 501 cgctgtttta attattcacc ttggtggtac ctttgaagga aaaaaagaaa 551 cattggatag gtttcgtaaa aattatcaac gcttgtctga ttcggttaaa 601 gctcgtttag ttttagaaaa cgatgatgtt tcttggtcag ttcaagattt 651 attaccttta tgccaagaac ttaatattcc tctagttttg gattggcatc 701 atcacaacat agtgccagga acgcttcgtg aaggaagttt agatttaatg 751 ccattaatcc caactattcg agaaacctgg acaagaaagg gaattacaca 801 gaagcaacat tactcagaat cggctgatcc aacggcgatt tctgggatga 851 aacgacgtgc tcactctgat agggtgtttg actttccacc gtgtgatcct 901 acaatggatc taatgataga agctaaggaa aaggaacagg ctgtatttga 951 attgtgtaga cgttatgagt tacaaaatcc accatgtcct cttgaaatta 1001 tggggcctga atacgatcaa actcgagatg gatattatcc gcccggagct 1051 gaaaagcgtt taactgcaag aaaaaggcgt agtagaaaag aagaagtaga 1101 agaggatgaa aaataaaaat ccgtcatact ttttgattta tggcataatt 1151 tagccatctc c

TABLE 8 Deduced Amino Acid Sequence of Δ228-UVDE (SEQ ID NO:4) 1 ddhapremfd cldkpipwrg rlgyaclnti lrsmkervfc srtcrittiq 51 rdglesvkql gtqnvldlik lvewnhnfgi hfmrvssdlf pfashakygy 101 tlefaqshle evgklankyn hrltmhpgqy tqiasprevv vdsairdlay 151 hdeilsrmkl neqlnkdavl iihlggtfeg kketldrfrk nyqrlsdsvk 201 arlvlenddv swsvqdllpl cqelniplvl dwhhhnivpg tlregsldlm 251 pliptiretw trkgitqkqh ysesadptai sgmkrrahsd rvfdfppcdp 301 tmdlmieake keqavfelcr ryelqnppcp leimgpeydq trdgyyppga 351 ekrltarkrr srkeeveede k

TABLE 9 Nucleotide Sequence Encoding GST-Δ228-UVDE (SEQ ID NO:5) 1 atgaccaagt tacctatact aggttattgg aaaaattaag ggccttgtgc 51 aacccactcg acttcttttg gaatatcttg aagaaaaata tgaagagcat 101 ttgtatgagc gcgatgaagg tgataaatgg cgaaacaaaa agtttgaatt 151 gggtttggag tttcccaatc ttccttatta tattgatggt gatgttaaat 201 taacacagtc tatggccatc atacgttata tagctgacaa gcacaacatg 251 ttggttggtt gtccaaaaga gcgtgcagag atttcaatgc ttgaaggagc 301 ggttttggat attagatacg gtgtttcgag aattgcatat agtaaagact 351 ttgaaactct caaagttgat tttcttagca agctacctga aatgctgaaa 401 atgttcgaag atcgtttatg tcataaaaca tatttaaatg ttgaccatgt 451 aacccatcct gacttcatgt tgtatgacgc tcttgatgtt gttttataca 501 tggacccaat gtgcctggat gcgttcccaa aattagtttg ttttaaaaaa 551 cgtattgaag ctatcccaca aattgataag tacttgaaat ccagcaagta 601 tatagcatgg cctttgcagg gctggcaagc cacgtttggt ggtggcgacc 651 atcctccaaa atcggatcat ctggttccgc gtggatccga tgatcatgct 701 ccacgagaga tgtttgattg tttggacaaa cccataccct ggcgaggacg 751 attggggtat gcttgtttga atactatttt aaggtcaatg aaggagaggg 801 ttttttgttc acgcacctgc cgaattacaa ccattcaacg tgatgggctc 851 gaaagtgtca agcagctagg tacgcaaaat gttttagatt taatcaaatt 901 ggttgagtgg aatcacaact ttggcattca cttcatgaga gtgagttctg 951 atttatttcc tttcgcaagc catgcaaagt atggatatac ccttgaattt 1001 gcacaatctc atctcgagga ggtgggcaag ctggcaaata aatataatca 1051 tcgattgact atgcatcctg gtcagtacac ccagatagcc tctccacgag 1101 aagtcgtagt tgattcggca atacgtgatt tggcttatca tgatgaaatt 1151 ctcagtcgta tgaagttgaa tgaacaatta aataaagacg ctgttttaat 1201 tattcacctt ggtggtacct ttgaaggaaa aaaagaaaca ttggataggt 1251 ttcgtaaaaa ttatcaacgc ttgtctgatt cggttaaagc tcgtttagtt 1301 ttagaaaacg atgatgtttc ttggtcagtt caagatttat tacctttatg 1351 ccaagaactt aatattcctc tagttttgga ttggcatcat cacaacatag 1401 tgccaggaac gcttcgtgaa ggaagtttag atttaatgcc attaatccca 1451 actattcgag aaacctggac aagaaaggga attacacaga agcaacatta 1501 ctcagaatcg gctgatccaa cggcgatttc tgggatgaaa cgacgtgctc 1551 actctgatag ggtgtttgac tttccaccgt gtgatcctac aatggatcta 1601 atgatagaag ctaaggaaaa ggaacaggct gtatttgaat tgtgtagacg 1651 ttatgagtta caaaatccac catgtcctct tgaaattatg gggcctgaat 1701 acgatcaaac tcgagatgga tattatccgc ccggagctga aaagcgttta 1751 actgcaagaa aaaggcgtag tagaaaagaa gaagtagaag aggatgaaaa 1801 ataaggatcc c

TABLE 10 Deduced Amino Acid Sequence of GST-Δ228-UVDE (SEQ ID NO:6) 1 mtklpilgyw kikglvqptr llleyleeky eehlyerdeg dkwrnkkfel 51 glefpnlpyy idgdvkitqs maiiryiadk hnmlggcpke raeismlega 101 vldirygvsr iayskdfetl kvdflsklpe mlkmfedrlc hktylngdhv 151 thpdfmlyda ldvvlymdpm cldafpkivc fkkrieaipq idkylkssky 201 iawplqgwqa tfgggdhppk sdhlvprgsd dhapremfdc idkpipwrgr 251 lgyaclntil rsmkervfcs rtcrittiqr dglesvkqlg tqnvldlikl 301 vewnhnfgih fmrvssdlfp fashakygyt lefaqshlee vgklankynh 351 rltmhpgqyt qiasprevvv dsairdlayh deilsrmkln eqlnkdavli 401 ihiggtfegk ketldrfrkn yqrlsdsvka rivlenddvs wsvqdllplc 451 qelniplvld whhhnivpgt lregsldlmp liptiretwt rkgitqkqhy 501 sesadptais gmkrrahsdr vfdfppcdpt mdlmieakek eqavfelcrr 551 yelqnppcpl eimgpeydqt rdgyyppgae krltarkrrs rkeeveedek

TABLE 11 Nucleotide Sequence Encoding the GST Leader Sequence (SEQ ID NO:7) 1 atgaccaagt tacctatact aggttattgg aaaaattaag ggccttgtgc 51 aacccactcg acttcttttg gaatatcttg aagaaaaata tgaagagcat 101 ttgtatgagc gcgatgaagg tgataaatgg cgaaacaaaa agtttgaatt 151 gggtttggag tttcccaatc ttccttatta tattgatggt gatgttaaat 201 taacacagtc tatggccatc atacgttata tagctgacaa gcacaacatg 251 ttggttggtt gtccaaaaga gcgtgcagag atttcaatgc ttgaaggagc 301 ggttttggat attagatacg gtgtttcgag aattgcatat agtaaagact 351 ttgaaactct caaagttgat tttcttagca agctacctga aatgctgaaa 401 atgttcgaag atcgtttatg tcataaaaca tatttaaatg ttgaccatgt 451 aacccatcct gacttcatgt tgtatgacgc tcttgatgtt gttttataca 501 tggacccaat gtgcctggat gcgttcccaa aattagtttg ttttaaaaaa 551 cgtattgaag ctatcccaca aattgataag tacttgaaat ccagcaagta 601 tatagcatgg cctttgcagg gctggcaagc cacgtttggt ggtggcgacc 651 atcctccaaa atcggatcat ctggttccgc gtggatcc

TABLE 12 Deduced Amino Acid Sequence of the GST Leader Polypeptide (SEQ ID NO:8) 1 MTKLPILGYW KIKGLVQPTR LLLEYLEEKY EEHLYERDEG DKWRNKKFEL 51 GLEFPNLPYY IDGDVKLTQS MAIIRYIADK HNMLGGCPKE RAEISMLEGA 101 VLDIRYGVSR IAYSKDFETL KVDFLSKLPE MLKMFEDRLC HKTYLNGDHV 151 THPDFMLYDA LDVVLYMDPM CLDAFPKLVC FKKRIEAIPQ IDKYLKSSKY 201 IAWPLQGWQA TFGGGDHPPK SDHLVPRGS

TABLE 13 Neurospora crassa UVDE Homolog (Genbank Accession No. BAA 74539) mpsrkskaaaldtpqsesstfsstldssapsparnlrrsgmilqpssekdrdhekrsgeelagrmmgkda (SEQ ID NO:36) nghclregkeqeegvkmaieglarmerrlqratkrqkkqleedgipvpsvvsrfptapyhhkstnaeere akepvlkthskdvereaeigvddvvkmepaatniiepedaqdaaergaarppavnssylplpwkgrlg yaclntylmskppifssrtermasivdhrhplqfedepehhlknkpdkskepqdelghkfvqelglanar divkmlewnekygirflrlssemfpfashpvhgyklapfasevlaeagrvaaelghrltthpgqftglgsp rkevvesairdleyhdellsllklpeqqnrdavmiihmggqfgdkaatlerfkrnyarlsqscknrlvlend dvgwtvhdllpvceelnipmvldhhhnicfdpahlregtldisdpklqeriantwkrkgikqkmhyse pedgavtprhrrkhrprvmtlppcppdmdlmieakdkeqavfelmrtfklpgfekindmvpydrdde nrpappvkapkkkkggkrkrttdeeaaepeevdtaaddvkdapegpkevpeeeramggpynrvyw plgceewlkpkkrevkkgkvpeevvedegefdg

TABLE 14 Bacillus subtilis UVDE Homolog (Genbank Accession No. Z 49782) mifrfgfvsnamslwdaspaktltfarysklskterkealltvtkanlrntmrtlhyiighgiplyrfsssivpl (SEQ ID NO:37) athpdvmwdfvtpfqkefreigelvkthqlrtsfhpnqftlftspkesvtknavtdmayhyrmleamgia drsvinihiggaygnkdtataqfhqnikqlpqeikermtlenddktytteetlqvceqedvpfvfdfhhfy akqkdkallrlmdelssirgvkrigggalqwks

TABLE 15 Human UVDE Homolog (Genbank Accession No. AF 114784.1) 1 mgttglesls lgdrgaaptv tsserlvpdp pndlrkedva melervgede egmmikrsse (SEQ ID NO:38) 61 cnpilqepia saqfgatagt ecrksvpcgw ervvkqrifg ktagrfdvyf ispqglkfrs 121 ksslany1hk ngetslkped fdftvlskrg iksrykdcsm aaltshlqnq snnsnwnlrt 181 rskckkdvfm ppsssselqe srglsnftst hlllkedegv ddvnfrkvrk pkgkvtilkg 241 ipikktkkgc rkscsgfvqs dskresvcnk adaesepvaq ksqldrtvci sdagacgetl 301 svtseenslv kkkerslssg snfcseqkts giinkfcsak dsehnekyed tf1eseeigt 361 kvevverkeh lhtdilkrgs emdnncsptr kdftgekifq edtiprtqie rrktslyfss 421 kynkealspp rrkafkkwtp prspfnlvqe tlfhdpwkll iatiflnrts gkmaipvlwk 481 flekypsaev artadwrdvs ellkplglyd lraktivkfs deyltkqwky pielhgigky 541 gndsyrifcv newkgvhped hklnkyhdwl wenheklsls

TABLE 16 D. radiodurans UVDE Homolog 1 QLGLVCLTVG PEVRFRTVTL SRYRALSPAE REAKLLDLYS SNIKTLRGAA (SEQ ID NO:39) 51 DYCAAHPIRL YRLSSSLFPM LDLAGDDTGA AVLTHLAPQL LEAGHAFTDA 101 GVRLLMHPEQ FIVLNSDRPE VRESSVRAMS AHARVMDGLG LARTFWNLLL 151 LHGGKGGRGA ELAALIPDLP DPVRLRLGLE NDERAYSPAE LLPICEATGT 261 PLVFDAHHHV VHDKLPDQED PSVREWVLRA RATWQPPEWQ VVHLSNGIEG 251 PQDRRHSHLI ADFPSAYADV PWIEVEAKGK EEAIAALRLM APFK

39 1 2492 DNA Artificial Sequence Description of Artificial Sequencefusion of a GST signal peptide and the UVDE protein of Schizosaccharomyces pombe 1 atgaccaagt tacctatact aggttattgg aaaaattaag ggccttgtgc aacccactcg 60 acttcttttg gaatatcttg aagaaaaata tgaagagcat ttgtatgagc gcgatgaagg 120 tgataaatgg cgaaacaaaa agtttgaatt gggtttggag tttcccaatc ttccttatta 180 tattgatggt gatgttaaat taacacagtc tatggccatc atacgttata tagctgacaa 240 gcacaacatg ttggttggtt gtccaaaaga gcgtgcagag atttcaatgc ttgaaggagc 300 ggttttggat attagatacg gtgtttcgag aattgcatat agtaaagact ttgaaactct 360 caaagttgat tttcttagca agctacctga aatgctgaaa atgttcgaag atcgtttatg 420 tcataaaaca tatttaaatg ttgaccatgt aacccatcct gacttcatgt tgtatgacgc 480 tcttgatgtt gttttataca tggacccaat gtgcctggat gcgttcccaa aattagtttg 540 ttttaaaaaa cgtattgaag ctatcccaca aattgataag tacttgaaat ccagcaagta 600 tatagcatgg cctttgcagg gctggcaagc cacgtttggt ggtggcgacc atcctccaaa 660 atcggatcat ctggttccgc gtggatccat gcttaggcta ttgaaacgaa atattcaaat 720 ctctaaacgc attgttttca ccatattaaa acaaaaggca tttaaaggta atcatccttg 780 tgtaccgtcg gtttgtacca ttacttactc tcgttttcat tgtttacccg atacccttaa 840 aagtttactt ccaatgagct caaaaaccac actctcaatg ttaccgcaag ttaatatcgg 900 tgcgaattca ttctctgccg aaacaccagt cgacttaaaa aaagaaaatg agactgagtt 960 agctaatatc agtggacctc acaaaaaaag tacttctacg tctacacgaa agagggcacg 1020 tagcagtaaa aagaaagcga cagattctgt ttccgataaa attgatgagt ctgttgcgtc 1080 ctatgattct tcaactcatc ttaggcgatc gtcgagatca aaaaaaccgg tcaactacaa 1140 ttcctcgtca gaatccgaat cggaggagca aattagtaaa gctactaaaa aagttaaaca 1200 aaaagaggaa gaggagtatg ttgaagaagt cgacgaaaag tctcttaaaa atgaaagtag 1260 ctctgacgag ttcgaaccgg ttgtgccgga acagttggaa actccaattt ctaaacgaag 1320 acggtctcgt tcttctgcaa aaaatttaga aaaagaatct acaatgaatc ttgatgatca 1380 tgctccacga gagatgtttg attgtttgga caaacccata ccctggcgag gacgattggg 1440 gtatgcttgt ttgaatacta ttttaaggtc aatgaaggag agggtttttt gttcacgcac 1500 ctgccgaatt acaaccattc aacgtgatgg gctcgaaagt gtcaagcagc taggtacgca 1560 aaatgtttta gatttaatca aattggttga gtggaatcac aactttggca ttcacttcat 1620 gagagtgagt tctgatttat ttcctttcgc aagccatgca aagtatggat atacccttga 1680 atttgcacaa tctcatctcg aggaggtggg caagctggca aataaatata atcatcgatt 1740 gactatgcat cctggtcagt acacccagat agcctctcca cgagaagtcg tagttgattc 1800 ggcaatacgt gatttggctt atcatgatga aattctcagt cgtatgaagt tgaatgaaca 1860 attaaataaa gacgctgttt taattattca ccttggtggt acctttgaag gaaaaaaaga 1920 aacattggat aggtttcgta aaaattatca acgcttgtct gattcggtta aagctcgttt 1980 agttttagaa aacgatgatg tttcttggtc agttcaagat ttattacctt tatgccaaga 2040 acttaatatt cctctagttt tggattggca tcatcacaac atagtgccag gaacgcttcg 2100 tgaaggaagt ttagatttaa tgccattaat cccaactatt cgagaaacct ggacaagaaa 2160 gggaattaca cagaagcaac attactcaga atcggctgat ccaacggcga tttctgggat 2220 gaaacgacgt gctcactctg atagggtgtt tgactttcca ccgtgtgatc ctacaatgga 2280 tctaatgata gaagctaagg aaaaggaaca ggctgtattt gaattgtgta gacgttatga 2340 gttacaaaat ccaccatgtc ctcttgaaat tatggggcct gaatacgatc aaactcgaga 2400 tggatattat ccgcccggag ctgaaaagcg tttaactgca agaaaaaggc gtagtagaaa 2460 agaagaagta gaagaggatg aaaaataaaa at 2492 2 828 PRT Artificial Sequence Description of Artificial Sequencefusion protein (GST leader peptide and Schizosaccharomyces pombe UVDE 2 Met Thr Lys Leu Pro Ile Leu Gly Tyr Trp Lys Ile Lys Gly Leu Val 1 5 10 15 Gln Pro Thr Arg Leu Leu Leu Glu Tyr Leu Glu Glu Lys Tyr Glu Glu 20 25 30 His Leu Tyr Glu Arg Asp Glu Gly Asp Lys Trp Arg Asn Lys Lys Phe 35 40 45 Glu Leu Gly Leu Glu Phe Pro Asn Leu Pro Tyr Tyr Ile Asp Gly Asp 50 55 60 Val Lys Leu Thr Gln Ser Met Ala Ile Ile Arg Tyr Ile Ala Asp Lys 65 70 75 80 His Asn Met Leu Gly Gly Cys Pro Lys Glu Arg Ala Glu Ile Ser Met 85 90 95 Leu Glu Gly Ala Val Leu Asp Ile Arg Tyr Gly Val Ser Arg Ile Ala 100 105 110 Tyr Ser Lys Asp Phe Glu Thr Leu Lys Val Asp Phe Leu Ser Lys Leu 115 120 125 Pro Glu Met Leu Lys Met Phe Glu Asp Arg Leu Cys His Lys Thr Tyr 130 135 140 Leu Asn Gly Asp His Val Thr His Pro Asp Phe Met Leu Tyr Asp Ala 145 150 155 160 Leu Asp Val Val Leu Tyr Met Asp Pro Met Cys Leu Asp Ala Phe Pro 165 170 175 Lys Leu Val Cys Phe Lys Lys Arg Ile Glu Ala Ile Pro Gln Ile Asp 180 185 190 Lys Tyr Leu Lys Ser Ser Lys Tyr Ile Ala Trp Pro Leu Gln Gly Trp 195 200 205 Gln Ala Thr Phe Gly Gly Gly Asp His Pro Pro Lys Ser Asp His Leu 210 215 220 Val Pro Arg Gly Ser Met Leu Arg Leu Leu Lys Arg Asn Ile Gln Ile 225 230 235 240 Ser Lys Arg Ile Val Phe Thr Ile Leu Lys Gln Lys Ala Phe Lys Gly 245 250 255 Asn His Pro Cys Val Pro Ser Val Cys Thr Ile Thr Tyr Ser Arg Phe 260 265 270 His Cys Leu Pro Asp Thr Leu Lys Ser Leu Leu Pro Met Ser Ser Lys 275 280 285 Thr Thr Leu Ser Met Leu Pro Gln Val Asn Ile Gly Ala Asn Ser Phe 290 295 300 Ser Ala Glu Thr Pro Val Asp Leu Lys Lys Glu Asn Glu Thr Glu Leu 305 310 315 320 Ala Asn Ile Ser Gly Pro His Lys Lys Ser Thr Ser Thr Ser Thr Arg 325 330 335 Lys Arg Ala Arg Ser Ser Lys Lys Lys Ala Thr Asp Ser Val Ser Asp 340 345 350 Lys Ile Asp Glu Ser Val Ala Ser Tyr Asp Ser Ser Thr His Leu Arg 355 360 365 Arg Ser Ser Arg Ser Lys Lys Pro Val Asn Tyr Asn Ser Ser Ser Glu 370 375 380 Ser Glu Ser Glu Glu Gln Ile Ser Lys Ala Thr Lys Lys Val Lys Gln 385 390 395 400 Lys Glu Glu Glu Glu Tyr Val Glu Glu Val Asp Glu Lys Ser Leu Lys 405 410 415 Asn Glu Ser Ser Ser Asp Glu Phe Glu Pro Val Val Pro Glu Gln Leu 420 425 430 Glu Thr Pro Ile Ser Lys Arg Arg Arg Ser Arg Ser Ser Ala Lys Asn 435 440 445 Leu Glu Lys Glu Ser Thr Met Asn Leu Asp Asp His Ala Pro Arg Glu 450 455 460 Met Phe Asp Cys Leu Asp Lys Pro Ile Pro Trp Arg Gly Arg Leu Gly 465 470 475 480 Tyr Ala Cys Leu Asn Thr Ile Leu Arg Ser Met Lys Glu Arg Val Phe 485 490 495 Cys Ser Arg Thr Cys Arg Ile Thr Thr Ile Gln Arg Asp Gly Leu Glu 500 505 510 Ser Val Lys Gln Leu Gly Thr Gln Asn Val Leu Asp Leu Ile Lys Leu 515 520 525 Val Glu Trp Asn His Asn Phe Gly Ile His Phe Met Arg Val Ser Ser 530 535 540 Asp Leu Phe Pro Phe Ala Ser His Ala Lys Tyr Gly Tyr Thr Leu Glu 545 550 555 560 Phe Ala Gln Ser His Leu Glu Glu Val Gly Lys Leu Ala Asn Lys Tyr 565 570 575 Asn His Arg Leu Thr Met His Pro Gly Gln Tyr Thr Gln Ile Ala Ser 580 585 590 Pro Arg Glu Val Val Val Asp Ser Ala Ile Arg Asp Leu Ala Tyr His 595 600 605 Asp Glu Ile Leu Ser Arg Met Lys Leu Asn Glu Gln Leu Asn Lys Asp 610 615 620 Ala Val Leu Ile Ile His Leu Gly Gly Thr Phe Glu Gly Lys Lys Glu 625 630 635 640 Thr Leu Asp Arg Phe Arg Lys Asn Tyr Gln Arg Leu Ser Asp Ser Val 645 650 655 Lys Ala Arg Leu Val Leu Glu Asn Asp Asp Val Ser Trp Ser Val Gln 660 665 670 Asp Leu Leu Pro Leu Cys Gln Glu Leu Asn Ile Pro Leu Val Leu Asp 675 680 685 Trp His His His Asn Ile Val Pro Gly Thr Leu Arg Glu Gly Ser Leu 690 695 700 Asp Leu Met Pro Leu Ile Pro Thr Ile Arg Glu Thr Trp Thr Arg Lys 705 710 715 720 Gly Ile Thr Gln Lys Gln His Tyr Ser Glu Ser Ala Asp Pro Thr Ala 725 730 735 Ile Ser Gly Met Lys Arg Arg Ala His Ser Asp Arg Val Phe Asp Phe 740 745 750 Pro Pro Cys Asp Pro Thr Met Asp Leu Met Ile Glu Ala Lys Glu Lys 755 760 765 Glu Gln Ala Val Phe Glu Leu Cys Arg Arg Tyr Glu Leu Gln Asn Pro 770 775 780 Pro Cys Pro Leu Glu Ile Met Gly Pro Glu Tyr Asp Gln Thr Arg Asp 785 790 795 800 Gly Tyr Tyr Pro Pro Gly Ala Glu Lys Arg Leu Thr Ala Arg Lys Arg 805 810 815 Arg Ser Arg Lys Glu Glu Val Glu Glu Asp Glu Lys 820 825 3 1161 DNA Artificial Sequence Description of Artificial Sequencesequence encoding Schizosaccharomyces pombe UVDE protein beginning at amino acid 228 of the whole protein 3 gatgatcatg ctccacgaga gatgtttgat tgtttggaca aacccatacc ctggcgagga 60 cgattggggt atgcttgttt gaatactatt ttaaggtcaa tgaaggagag ggttttttgt 120 tcacgcacct gccgaattac aaccattcaa cgtgatgggc tcgaaagtgt caagcagcta 180 ggtacgcaaa atgttttaga tttaatcaaa ttggttgagt ggaatcacaa ctttggcatt 240 cacttcatga gagtgagttc tgatttattt cctttcgcaa gccatgcaaa gtatggatat 300 acccttgaat ttgcacaatc tcatctcgag gaggtgggca agctggcaaa taaatataat 360 catcgattga ctatgcatcc tggtcagtac acccagatag cctctccacg agaagtcgta 420 gttgattcgg caatacgtga tttggcttat catgatgaaa ttctcagtcg tatgaagttg 480 aatgaacaat taaataaaga cgctgtttta attattcacc ttggtggtac ctttgaagga 540 aaaaaagaaa cattggatag gtttcgtaaa aattatcaac gcttgtctga ttcggttaaa 600 gctcgtttag ttttagaaaa cgatgatgtt tcttggtcag ttcaagattt attaccttta 660 tgccaagaac ttaatattcc tctagttttg gattggcatc atcacaacat agtgccagga 720 acgcttcgtg aaggaagttt agatttaatg ccattaatcc caactattcg agaaacctgg 780 acaagaaagg gaattacaca gaagcaacat tactcagaat cggctgatcc aacggcgatt 840 tctgggatga aacgacgtgc tcactctgat agggtgtttg actttccacc gtgtgatcct 900 acaatggatc taatgataga agctaaggaa aaggaacagg ctgtatttga attgtgtaga 960 cgttatgagt tacaaaatcc accatgtcct cttgaaatta tggggcctga atacgatcaa 1020 actcgagatg gatattatcc gcccggagct gaaaagcgtt taactgcaag aaaaaggcgt 1080 agtagaaaag aagaagtaga agaggatgaa aaataaaaat ccgtcatact ttttgattta 1140 tggcataatt tagccatctc c 1161 4 371 PRT Artificial Sequence Description of Artificial Sequencetruncated derivative of the S. pombe UVDE protein 4 Asp Asp His Ala Pro Arg Glu Met Phe Asp Cys Leu Asp Lys Pro Ile 1 5 10 15 Pro Trp Arg Gly Arg Leu Gly Tyr Ala Cys Leu Asn Thr Ile Leu Arg 20 25 30 Ser Met Lys Glu Arg Val Phe Cys Ser Arg Thr Cys Arg Ile Thr Thr 35 40 45 Ile Gln Arg Asp Gly Leu Glu Ser Val Lys Gln Leu Gly Thr Gln Asn 50 55 60 Val Leu Asp Leu Ile Lys Leu Val Glu Trp Asn His Asn Phe Gly Ile 65 70 75 80 His Phe Met Arg Val Ser Ser Asp Leu Phe Pro Phe Ala Ser His Ala 85 90 95 Lys Tyr Gly Tyr Thr Leu Glu Phe Ala Gln Ser His Leu Glu Glu Val 100 105 110 Gly Lys Leu Ala Asn Lys Tyr Asn His Arg Leu Thr Met His Pro Gly 115 120 125 Gln Tyr Thr Gln Ile Ala Ser Pro Arg Glu Val Val Val Asp Ser Ala 130 135 140 Ile Arg Asp Leu Ala Tyr His Asp Glu Ile Leu Ser Arg Met Lys Leu 145 150 155 160 Asn Glu Gln Leu Asn Lys Asp Ala Val Leu Ile Ile His Leu Gly Gly 165 170 175 Thr Phe Glu Gly Lys Lys Glu Thr Leu Asp Arg Phe Arg Lys Asn Tyr 180 185 190 Gln Arg Leu Ser Asp Ser Val Lys Ala Arg Leu Val Leu Glu Asn Asp 195 200 205 Asp Val Ser Trp Ser Val Gln Asp Leu Leu Pro Leu Cys Gln Glu Leu 210 215 220 Asn Ile Pro Leu Val Leu Asp Trp His His His Asn Ile Val Pro Gly 225 230 235 240 Thr Leu Arg Glu Gly Ser Leu Asp Leu Met Pro Leu Ile Pro Thr Ile 245 250 255 Arg Glu Thr Trp Thr Arg Lys Gly Ile Thr Gln Lys Gln His Tyr Ser 260 265 270 Glu Ser Ala Asp Pro Thr Ala Ile Ser Gly Met Lys Arg Arg Ala His 275 280 285 Ser Asp Arg Val Phe Asp Phe Pro Pro Cys Asp Pro Thr Met Asp Leu 290 295 300 Met Ile Glu Ala Lys Glu Lys Glu Gln Ala Val Phe Glu Leu Cys Arg 305 310 315 320 Arg Tyr Glu Leu Gln Asn Pro Pro Cys Pro Leu Glu Ile Met Gly Pro 325 330 335 Glu Tyr Asp Gln Thr Arg Asp Gly Tyr Tyr Pro Pro Gly Ala Glu Lys 340 345 350 Arg Leu Thr Ala Arg Lys Arg Arg Ser Arg Lys Glu Glu Val Glu Glu 355 360 365 Asp Glu Lys 370 5 1811 DNA Artificial Sequence Description of Artificial Sequencenucleotide sequence encoding fusion protein (GST signal peptide fused to the truncated derivative of the S. pmbe UVDE protein) 5 atgaccaagt tacctatact aggttattgg aaaaattaag ggccttgtgc aacccactcg 60 acttcttttg gaatatcttg aagaaaaata tgaagagcat ttgtatgagc gcgatgaagg 120 tgataaatgg cgaaacaaaa agtttgaatt gggtttggag tttcccaatc ttccttatta 180 tattgatggt gatgttaaat taacacagtc tatggccatc atacgttata tagctgacaa 240 gcacaacatg ttggttggtt gtccaaaaga gcgtgcagag atttcaatgc ttgaaggagc 300 ggttttggat attagatacg gtgtttcgag aattgcatat agtaaagact ttgaaactct 360 caaagttgat tttcttagca agctacctga aatgctgaaa atgttcgaag atcgtttatg 420 tcataaaaca tatttaaatg ttgaccatgt aacccatcct gacttcatgt tgtatgacgc 480 tcttgatgtt gttttataca tggacccaat gtgcctggat gcgttcccaa aattagtttg 540 ttttaaaaaa cgtattgaag ctatcccaca aattgataag tacttgaaat ccagcaagta 600 tatagcatgg cctttgcagg gctggcaagc cacgtttggt ggtggcgacc atcctccaaa 660 atcggatcat ctggttccgc gtggatccga tgatcatgct ccacgagaga tgtttgattg 720 tttggacaaa cccataccct ggcgaggacg attggggtat gcttgtttga atactatttt 780 aaggtcaatg aaggagaggg ttttttgttc acgcacctgc cgaattacaa ccattcaacg 840 tgatgggctc gaaagtgtca agcagctagg tacgcaaaat gttttagatt taatcaaatt 900 ggttgagtgg aatcacaact ttggcattca cttcatgaga gtgagttctg atttatttcc 960 tttcgcaagc catgcaaagt atggatatac ccttgaattt gcacaatctc atctcgagga 1020 ggtgggcaag ctggcaaata aatataatca tcgattgact atgcatcctg gtcagtacac 1080 ccagatagcc tctccacgag aagtcgtagt tgattcggca atacgtgatt tggcttatca 1140 tgatgaaatt ctcagtcgta tgaagttgaa tgaacaatta aataaagacg ctgttttaat 1200 tattcacctt ggtggtacct ttgaaggaaa aaaagaaaca ttggataggt ttcgtaaaaa 1260 ttatcaacgc ttgtctgatt cggttaaagc tcgtttagtt ttagaaaacg atgatgtttc 1320 ttggtcagtt caagatttat tacctttatg ccaagaactt aatattcctc tagttttgga 1380 ttggcatcat cacaacatag tgccaggaac gcttcgtgaa ggaagtttag atttaatgcc 1440 attaatccca actattcgag aaacctggac aagaaaggga attacacaga agcaacatta 1500 ctcagaatcg gctgatccaa cggcgatttc tgggatgaaa cgacgtgctc actctgatag 1560 ggtgtttgac tttccaccgt gtgatcctac aatggatcta atgatagaag ctaaggaaaa 1620 ggaacaggct gtatttgaat tgtgtagacg ttatgagtta caaaatccac catgtcctct 1680 tgaaattatg gggcctgaat acgatcaaac tcgagatgga tattatccgc ccggagctga 1740 aaagcgttta actgcaagaa aaaggcgtag tagaaaagaa gaagtagaag aggatgaaaa 1800 ataaggatcc c 1811 6 600 PRT Artificial Sequence Description of Artificial Sequencefusion protein comprising the GST signal peptide and the truncated UVDE protein of S. pombe 6 Met Thr Lys Leu Pro Ile Leu Gly Tyr Trp Lys Ile Lys Gly Leu Val 1 5 10 15 Gln Pro Thr Arg Leu Leu Leu Glu Tyr Leu Glu Glu Lys Tyr Glu Glu 20 25 30 His Leu Tyr Glu Arg Asp Glu Gly Asp Lys Trp Arg Asn Lys Lys Phe 35 40 45 Glu Leu Gly Leu Glu Phe Pro Asn Leu Pro Tyr Tyr Ile Asp Gly Asp 50 55 60 Val Lys Leu Thr Gln Ser Met Ala Ile Ile Arg Tyr Ile Ala Asp Lys 65 70 75 80 His Asn Met Leu Gly Gly Cys Pro Lys Glu Arg Ala Glu Ile Ser Met 85 90 95 Leu Glu Gly Ala Val Leu Asp Ile Arg Tyr Gly Val Ser Arg Ile Ala 100 105 110 Tyr Ser Lys Asp Phe Glu Thr Leu Lys Val Asp Phe Leu Ser Lys Leu 115 120 125 Pro Glu Met Leu Lys Met Phe Glu Asp Arg Leu Cys His Lys Thr Tyr 130 135 140 Leu Asn Gly Asp His Val Thr His Pro Asp Phe Met Leu Tyr Asp Ala 145 150 155 160 Leu Asp Val Val Leu Tyr Met Asp Pro Met Cys Leu Asp Ala Phe Pro 165 170 175 Lys Leu Val Cys Phe Lys Lys Arg Ile Glu Ala Ile Pro Gln Ile Asp 180 185 190 Lys Tyr Leu Lys Ser Ser Lys Tyr Ile Ala Trp Pro Leu Gln Gly Trp 195 200 205 Gln Ala Thr Phe Gly Gly Gly Asp His Pro Pro Lys Ser Asp His Leu 210 215 220 Val Pro Arg Gly Ser Asp Asp His Ala Pro Arg Glu Met Phe Asp Cys 225 230 235 240 Leu Asp Lys Pro Ile Pro Trp Arg Gly Arg Leu Gly Tyr Ala Cys Leu 245 250 255 Asn Thr Ile Leu Arg Ser Met Lys Glu Arg Val Phe Cys Ser Arg Thr 260 265 270 Cys Arg Ile Thr Thr Ile Gln Arg Asp Gly Leu Glu Ser Val Lys Gln 275 280 285 Leu Gly Thr Gln Asn Val Leu Asp Leu Ile Lys Leu Val Glu Trp Asn 290 295 300 His Asn Phe Gly Ile His Phe Met Arg Val Ser Ser Asp Leu Phe Pro 305 310 315 320 Phe Ala Ser His Ala Lys Tyr Gly Tyr Thr Leu Glu Phe Ala Gln Ser 325 330 335 His Leu Glu Glu Val Gly Lys Leu Ala Asn Lys Tyr Asn His Arg Leu 340 345 350 Thr Met His Pro Gly Gln Tyr Thr Gln Ile Ala Ser Pro Arg Glu Val 355 360 365 Val Val Asp Ser Ala Ile Arg Asp Leu Ala Tyr His Asp Glu Ile Leu 370 375 380 Ser Arg Met Lys Leu Asn Glu Gln Leu Asn Lys Asp Ala Val Leu Ile 385 390 395 400 Ile His Leu Gly Gly Thr Phe Glu Gly Lys Lys Glu Thr Leu Asp Arg 405 410 415 Phe Arg Lys Asn Tyr Gln Arg Leu Ser Asp Ser Val Lys Ala Arg Leu 420 425 430 Val Leu Glu Asn Asp Asp Val Ser Trp Ser Val Gln Asp Leu Leu Pro 435 440 445 Leu Cys Gln Glu Leu Asn Ile Pro Leu Val Leu Asp Trp His His His 450 455 460 Asn Ile Val Pro Gly Thr Leu Arg Glu Gly Ser Leu Asp Leu Met Pro 465 470 475 480 Leu Ile Pro Thr Ile Arg Glu Thr Trp Thr Arg Lys Gly Ile Thr Gln 485 490 495 Lys Gln His Tyr Ser Glu Ser Ala Asp Pro Thr Ala Ile Ser Gly Met 500 505 510 Lys Arg Arg Ala His Ser Asp Arg Val Phe Asp Phe Pro Pro Cys Asp 515 520 525 Pro Thr Met Asp Leu Met Ile Glu Ala Lys Glu Lys Glu Gln Ala Val 530 535 540 Phe Glu Leu Cys Arg Arg Tyr Glu Leu Gln Asn Pro Pro Cys Pro Leu 545 550 555 560 Glu Ile Met Gly Pro Glu Tyr Asp Gln Thr Arg Asp Gly Tyr Tyr Pro 565 570 575 Pro Gly Ala Glu Lys Arg Leu Thr Ala Arg Lys Arg Arg Ser Arg Lys 580 585 590 Glu Glu Val Glu Glu Asp Glu Lys 595 600 7 688 DNA Artificial Sequence Description of Artificial Sequencenucleotide sequence encoding GST signal (leader) peptide 7 atgaccaagt tacctatact aggttattgg aaaaattaag ggccttgtgc aacccactcg 60 acttcttttg gaatatcttg aagaaaaata tgaagagcat ttgtatgagc gcgatgaagg 120 tgataaatgg cgaaacaaaa agtttgaatt gggtttggag tttcccaatc ttccttatta 180 tattgatggt gatgttaaat taacacagtc tatggccatc atacgttata tagctgacaa 240 gcacaacatg ttggttggtt gtccaaaaga gcgtgcagag atttcaatgc ttgaaggagc 300 ggttttggat attagatacg gtgtttcgag aattgcatat agtaaagact ttgaaactct 360 caaagttgat tttcttagca agctacctga aatgctgaaa atgttcgaag atcgtttatg 420 tcataaaaca tatttaaatg ttgaccatgt aacccatcct gacttcatgt tgtatgacgc 480 tcttgatgtt gttttataca tggacccaat gtgcctggat gcgttcccaa aattagtttg 540 ttttaaaaaa cgtattgaag ctatcccaca aattgataag tacttgaaat ccagcaagta 600 tatagcatgg cctttgcagg gctggcaagc cacgtttggt ggtggcgacc atcctccaaa 660 atcggatcat ctggttccgc gtggatcc 688 8 229 PRT Artificial Sequence Description of Artificial Sequenceamino acid sequence of the GST leader peptide 8 Met Thr Lys Leu Pro Ile Leu Gly Tyr Trp Lys Ile Lys Gly Leu Val 1 5 10 15 Gln Pro Thr Arg Leu Leu Leu Glu Tyr Leu Glu Glu Lys Tyr Glu Glu 20 25 30 His Leu Tyr Glu Arg Asp Glu Gly Asp Lys Trp Arg Asn Lys Lys Phe 35 40 45 Glu Leu Gly Leu Glu Phe Pro Asn Leu Pro Tyr Tyr Ile Asp Gly Asp 50 55 60 Val Lys Leu Thr Gln Ser Met Ala Ile Ile Arg Tyr Ile Ala Asp Lys 65 70 75 80 His Asn Met Leu Gly Gly Cys Pro Lys Glu Arg Ala Glu Ile Ser Met 85 90 95 Leu Glu Gly Ala Val Leu Asp Ile Arg Tyr Gly Val Ser Arg Ile Ala 100 105 110 Tyr Ser Lys Asp Phe Glu Thr Leu Lys Val Asp Phe Leu Ser Lys Leu 115 120 125 Pro Glu Met Leu Lys Met Phe Glu Asp Arg Leu Cys His Lys Thr Tyr 130 135 140 Leu Asn Gly Asp His Val Thr His Pro Asp Phe Met Leu Tyr Asp Ala 145 150 155 160 Leu Asp Val Val Leu Tyr Met Asp Pro Met Cys Leu Asp Ala Phe Pro 165 170 175 Lys Leu Val Cys Phe Lys Lys Arg Ile Glu Ala Ile Pro Gln Ile Asp 180 185 190 Lys Tyr Leu Lys Ser Ser Lys Tyr Ile Ala Trp Pro Leu Gln Gly Trp 195 200 205 Gln Ala Thr Phe Gly Gly Gly Asp His Pro Pro Lys Ser Asp His Leu 210 215 220 Val Pro Arg Gly Ser 225 9 36 DNA Artificial Sequence Description of Artificial Sequence oligonucleotide used in polymerase chain reaction. 9 tgaggatcca atcgttttca ttttttaatg cttagg 36 10 23 DNA Artificial Sequence Description of Artificial Sequence oligonucleotide used in polymerase chain reaction. 10 ggccatggtt atttttcatc ctc 23 11 28 DNA Artificial Sequence Description of Artificial Sequence oligonucleotide used in polymerase chain reaction 11 aatgggatcc gatgatcatg ctccacga 28 12 28 DNA Artificial Sequence Description of Artificial Sequence oligonucleotide used in polymerase chain reaction 12 gggatcctta tttttcatcc tcttctac 28 13 30 DNA Artificial Sequence Description of Artificial Sequencedouble stranded oligonucleotide containing cis-syn cyclobutane pyrimidine dimer 13 catgcctgca cgaattaagc aattcgtaat 30 14 30 DNA Artificial Sequence Description of Artificial Sequenceundamaged double stranded oligonucleotide 14 catgcctgca cgaattaagc aattcgtaat 30 15 49 DNA Artificial Sequence Description of Artificial Sequencedouble stranded oligonucleotide containing cis-syn cyclobutane dimer at positions 21-22 15 agctaccatg cctgcacgaa ttaagcaatt cgtaatcatg gtcatagct 49 16 49 DNA Artificial Sequence Description of Artificial Sequencedouble stranded oligonucleotide containing cis-syn cyclobutane pyrimidine dimer at positions 21-22. 16 agctaccatg cctgcacgaa ttaagcaatt cgtaatcatg gtcatagct 49 17 49 DNA Artificial Sequence Description of Artificial Sequencedouble stranded oligonucleotide containing trans-syn II cyclobutane pyrimidine dimer at positions 21-22 17 agctaccatg cctgcacgaa ttaagcaatt cgtaatcatg gtcatagct 49 18 49 DNA Artificial Sequence Description of Artificial Sequencedouble stranded oligonucleotide containing a 6-4 photoproduct 18 agctaccatg cctgcacgaa ttaagcaatt cgtaatcatg gtcatagct 49 19 49 DNA Artificial Sequence Description of Artificial Sequencedouble stranded oligonucleotide containing Dewar isomer 19 agctaccatg cctgcacgaa ttaagcaatt cgtaatcatg gtcatagct 49 20 32 DNA Artificial Sequence Description of Artificial Sequencedouble stranded oligonucleotide containing cisplatin DNA diadduct 20 tccctccttc cttccggccc tccttcccct tc 32 21 37 DNA Artificial Sequence Description of Artificial Sequencedouble stranded oligonucleotide wherein n is uracil 21 cttggactgg atgtcggcac nagcggatac aggagca 37 22 37 DNA Artificial Sequence Description of Artificial Sequencedouble stranded oligonucleotide wherein n is dihydrouracil 22 cttggactgg atgtcggcac nagcggatac aggagca 37 23 37 DNA Artificial Sequence Description of Artificial Sequencedouble stranded oligonucleotide wherein n at postion 21 represents an abasic site 23 cttggactgg atgtcggcac nagcggatac aggagca 37 24 31 DNA Artificial Sequence Description of Artificial Sequencedouble stranded oligonucleotide wherein n at position 13 is an inosine 24 tgcaggtcga ctnaggagga tccccgggta c 31 25 31 DNA Artificial Sequence Description of Artificial Sequencedouble stranded oligonucleotide wherein n at position 13 represents xanthine 25 tgcaggtcga ctnaggagga tccccgggta c 31 26 37 DNA Artificial Sequence Description of Artificial Sequencedouble stranded oligonucleotide wherein position 21 is 8-oxoguanine 26 cttggactgg atgtcggcac nagcggatac aggagca 37 27 30 DNA Artificial Sequence Description of Artificial Sequencedouble stranded oligonucleotide representing all 16 possible base pair mismatches at position 18 in individual preparations 27 gtacccgggg atcctccnag tcgacctgca 30 28 41 DNA Artificial Sequence Description of Artificial Sequencedouble stranded oligonucleotide containing a CA mismatched base pair at position 21 28 cgttagcatg cctgcacgaa ntaagcaatt cgtaatgcat t 41 29 41 DNA Artificial Sequence Description of Artificial Sequencedouble stranded oligonucleotide wherein there is a C/A mismatched base pair at position 36 29 cgttacaagt ccgtcacgaa ttaagcaatt cgtaangcat t 41 30 41 DNA Artificial Sequence Description of Artificial Sequencedouble stranded oligonucleotide wherein position 31 is a C/A mimatched base pair 30 cgttacaagt ccgtcacgaa ttaagcaatt ngtaacgcat t 41 31 41 DNA Artificial Sequence Description of Artificial Sequencedouble stranded oligonucleotide wherein n at position 26 represents a C/A mismatched base pair 31 cgttacaagt ccgtcacgaa ttaagnaatt cgtaacgcat t 41 32 41 DNA Artificial Sequence Description of Artificial Sequencedouble stranded oligonucleotide wherein there is a C/A mismatched base pair at position 21. 32 cgttacaagt ccgtcacgac ntaagcaatt cgtaacgcat t 41 33 41 DNA Artificial Sequence Description of Artificial Sequencedouble stranded oligonucleotide wherein n at position 15 represents a C/A mismatched base pair 33 cgttacaagt ccgtnacgaa ttaagcaatt cgtaacgcat t 41 34 41 DNA Artificial Sequence Description of Artificial Sequencedouble stranded oligonucleotide wherein n at position 10 is a C/A mismatched base pair 34 cgttacaagn ccgtcacgaa ttaagcaatt cgtaacgcat t 41 35 41 DNA Artificial Sequence Description of Artificial Sequencedouble stranded oligonucleotide wherein n at position 5 is a C/A mismatched base pair 35 cgttncaagt ccgtcacgaa ttaagcaatt cgtaacgcat t 41 36 656 PRT Neurospora crassa 36 Met Pro Ser Arg Lys Ser Lys Ala Ala Ala Leu Asp Thr Pro Gln Ser 1 5 10 15 Glu Ser Ser Thr Phe Ser Ser Thr Leu Asp Ser Ser Ala Pro Ser Pro 20 25 30 Ala Arg Asn Leu Arg Arg Ser Gly Arg Asn Ile Leu Gln Pro Ser Ser 35 40 45 Glu Lys Asp Arg Asp His Glu Lys Arg Ser Gly Glu Glu Leu Ala Gly 50 55 60 Arg Met Met Gly Lys Asp Ala Asn Gly His Cys Leu Arg Glu Gly Lys 65 70 75 80 Glu Gln Glu Glu Gly Val Lys Met Ala Ile Glu Gly Leu Ala Arg Met 85 90 95 Glu Arg Arg Leu Gln Arg Ala Thr Lys Arg Gln Lys Lys Gln Leu Glu 100 105 110 Glu Asp Gly Ile Pro Val Pro Ser Val Val Ser Arg Phe Pro Thr Ala 115 120 125 Pro Tyr His His Lys Ser Thr Asn Ala Glu Glu Arg Glu Ala Lys Glu 130 135 140 Pro Val Leu Lys Thr His Ser Lys Asp Val Glu Arg Glu Ala Glu Ile 145 150 155 160 Gly Val Asp Asp Val Val Lys Met Glu Pro Ala Ala Thr Asn Ile Ile 165 170 175 Glu Pro Glu Asp Ala Gln Asp Ala Ala Glu Arg Gly Ala Ala Arg Pro 180 185 190 Pro Ala Val Asn Ser Ser Tyr Leu Pro Leu Pro Trp Lys Gly Arg Leu 195 200 205 Gly Tyr Ala Cys Leu Asn Thr Tyr Leu Arg Asn Ala Lys Pro Pro Ile 210 215 220 Phe Ser Ser Arg Thr Cys Arg Met Ala Ser Ile Val Asp His Arg His 225 230 235 240 Pro Leu Gln Phe Glu Asp Glu Pro Glu His His Leu Lys Asn Lys Pro 245 250 255 Asp Lys Ser Lys Glu Pro Gln Asp Glu Leu Gly His Lys Phe Val Gln 260 265 270 Glu Leu Gly Leu Ala Asn Ala Arg Asp Ile Val Lys Met Leu Cys Trp 275 280 285 Asn Glu Lys Tyr Gly Ile Arg Phe Leu Arg Leu Ser Ser Glu Met Phe 290 295 300 Pro Phe Ala Ser His Pro Val His Gly Tyr Lys Leu Ala Pro Phe Ala 305 310 315 320 Ser Glu Val Leu Ala Glu Ala Gly Arg Val Ala Ala Glu Leu Gly His 325 330 335 Arg Leu Thr Thr His Pro Gly Gln Phe Thr Gln Leu Gly Ser Pro Arg 340 345 350 Lys Glu Val Val Glu Ser Ala Ile Arg Asp Leu Glu Tyr His Asp Glu 355 360 365 Leu Leu Ser Leu Leu Lys Leu Pro Glu Gln Gln Asn Arg Asp Ala Val 370 375 380 Met Ile Ile His Met Gly Gly Gln Phe Gly Asp Lys Ala Ala Thr Leu 385 390 395 400 Glu Arg Phe Lys Arg Asn Tyr Ala Arg Leu Ser Gln Ser Cys Lys Asn 405 410 415 Arg Leu Val Leu Glu Asn Asp Asp Val Gly Trp Thr Val His Asp Leu 420 425 430 Leu Pro Val Cys Glu Glu Leu Asn Ile Pro Met Val Leu Asp Tyr His 435 440 445 His His Asn Ile Cys Phe Asp Pro Ala His Leu Arg Glu Gly Thr Leu 450 455 460 Asp Ile Ser Asp Pro Lys Leu Gln Glu Arg Ile Ala Asn Thr Trp Lys 465 470 475 480 Arg Lys Gly Ile Lys Gln Lys Met His Tyr Ser Glu Pro Cys Asp Gly 485 490 495 Ala Val Thr Pro Arg Asp Arg Arg Lys His Arg Pro Arg Val Met Thr 500 505 510 Leu Pro Pro Cys Pro Pro Asp Met Asp Leu Met Ile Glu Ala Lys Asp 515 520 525 Lys Glu Gln Ala Val Phe Glu Leu Met Arg Thr Phe Lys Leu Pro Gly 530 535 540 Phe Glu Lys Ile Asn Asp Met Val Pro Tyr Asp Arg Asp Asp Glu Asn 545 550 555 560 Arg Pro Ala Pro Pro Val Lys Ala Pro Lys Lys Lys Lys Gly Gly Lys 565 570 575 Arg Lys Arg Thr Thr Asp Glu Glu Ala Ala Glu Pro Glu Glu Val Asp 580 585 590 Thr Ala Ala Asp Asp Val Lys Asp Ala Pro Glu Gly Pro Lys Glu Val 595 600 605 Pro Glu Glu Glu Arg Ala Met Gly Gly Pro Tyr Asn Arg Val Tyr Trp 610 615 620 Pro Leu Gly Cys Glu Glu Trp Leu Lys Pro Lys Lys Arg Glu Val Lys 625 630 635 640 Lys Gly Lys Val Pro Glu Glu Val Glu Asp Glu Gly Glu Phe Asp Gly 645 650 655 37 317 PRT Bacillus subtilis 37 Met Ile Phe Arg Phe Gly Phe Val Ser Asn Ala Met Ser Leu Trp Asp 1 5 10 15 Ala Ser Pro Ala Lys Thr Leu Thr Phe Ala Arg Tyr Ser Lys Leu Ser 20 25 30 Lys Thr Glu Arg Lys Glu Ala Leu Leu Thr Val Thr Lys Ala Asn Leu 35 40 45 Arg Asn Thr Met Arg Thr Leu His Tyr Ile Ile Gly His Gly Ile Pro 50 55 60 Leu Tyr Arg Phe Ser Ser Ser Ile Val Pro Leu Ala Thr His Pro Asp 65 70 75 80 Val Met Trp Asp Phe Val Thr Pro Phe Gln Lys Glu Phe Arg Glu Ile 85 90 95 Gly Glu Leu Val Lys Thr His Gln Leu Arg Thr Ser Phe His Pro Asn 100 105 110 Gln Phe Thr Leu Phe Thr Ser Pro Lys Glu Ser Val Thr Lys Asn Ala 115 120 125 Val Thr Asp Met Ala Tyr His Tyr Arg Met Leu Glu Ala Met Gly Ile 130 135 140 Ala Asp Arg Ser Val Ile Asn Ile His Ile Gly Gly Ala Tyr Gly Asn 145 150 155 160 Lys Asp Thr Ala Thr Ala Gln Phe His Gln Asn Ile Lys Gln Leu Pro 165 170 175 Gln Glu Ile Lys Glu Arg Met Thr Leu Glu Asn Asp Asp Lys Thr Tyr 180 185 190 Thr Thr Glu Glu Thr Leu Gln Val Cys Glu Gln Glu Asp Val Pro Phe 195 200 205 Val Phe Asp Phe His His Phe Tyr Ala Asn Pro Asp Asp His Ala Asp 210 215 220 Leu Asn Val Ala Leu Pro Arg Met Ile Lys Thr Trp Glu Arg Ile Gly 225 230 235 240 Leu Gln Pro Lys Val His Leu Ser Ser Pro Lys Ser Glu Gln Ala Ile 245 250 255 Arg Ser His Ala Asp Tyr Val Asp Ala Asn Phe Leu Leu Glu Arg Phe 260 265 270 Arg Gln Trp Gly Thr Asn Ile Asp Phe Met Ile Glu Ala Lys Gln Lys 275 280 285 Asp Lys Ala Leu Leu Arg Leu Met Asp Glu Leu Ser Ser Ile Arg Gly 290 295 300 Val Lys Arg Ile Gly Gly Gly Ala Leu Gln Trp Lys Ser 305 310 315 38 580 PRT Homo sapiens 38 Met Gly Thr Thr Gly Leu Glu Ser Leu Ser Leu Gly Asp Arg Gly Ala 1 5 10 15 Ala Pro Thr Val Thr Ser Ser Glu Arg Leu Val Pro Asp Pro Pro Asn 20 25 30 Asp Leu Arg Lys Glu Asp Val Ala Met Glu Leu Glu Arg Val Gly Glu 35 40 45 Asp Glu Glu Gln Met Met Ile Lys Arg Ser Ser Glu Cys Asn Pro Leu 50 55 60 Leu Gln Glu Pro Ile Ala Ser Ala Gln Phe Gly Ala Thr Ala Gly Thr 65 70 75 80 Glu Cys Arg Lys Ser Val Pro Cys Gly Trp Glu Arg Val Val Lys Gln 85 90 95 Arg Leu Phe Gly Lys Thr Ala Gly Arg Phe Asp Val Tyr Phe Ile Ser 100 105 110 Pro Gln Gly Leu Lys Phe Arg Ser Lys Ser Ser Leu Ala Asn Tyr Leu 115 120 125 His Lys Asn Gly Glu Thr Ser Leu Lys Pro Glu Asp Phe Asp Phe Thr 130 135 140 Val Leu Ser Lys Arg Gly Ile Lys Ser Arg Tyr Lys Asp Cys Ser Met 145 150 155 160 Ala Ala Leu Thr Ser His Leu Gln Asn Gln Ser Asn Asn Ser Asn Trp 165 170 175 Asn Leu Arg Thr Arg Ser Lys Cys Lys Lys Asp Val Phe Met Pro Pro 180 185 190 Ser Ser Ser Ser Glu Leu Gln Glu Ser Arg Gly Leu Ser Asn Phe Thr 195 200 205 Ser Thr His Leu Leu Leu Lys Glu Asp Glu Gly Val Asp Asp Val Asn 210 215 220 Phe Arg Lys Val Arg Lys Pro Lys Gly Lys Val Thr Ile Leu Lys Gly 225 230 235 240 Ile Pro Ile Lys Lys Thr Lys Lys Gly Cys Arg Lys Ser Cys Ser Gly 245 250 255 Phe Val Gln Ser Asp Ser Lys Arg Glu Ser Val Cys Asn Lys Ala Asp 260 265 270 Ala Glu Ser Glu Pro Val Ala Gln Lys Ser Gln Leu Asp Arg Thr Val 275 280 285 Cys Ile Ser Asp Ala Gly Ala Cys Gly Glu Thr Leu Ser Val Thr Ser 290 295 300 Glu Glu Asn Ser Leu Val Lys Lys Lys Glu Arg Ser Leu Ser Ser Gly 305 310 315 320 Ser Asn Phe Cys Ser Glu Gln Lys Thr Ser Gly Ile Ile Asn Lys Phe 325 330 335 Cys Ser Ala Lys Asp Ser Glu His Asn Glu Lys Tyr Glu Asp Thr Phe 340 345 350 Leu Glu Ser Glu Glu Ile Gly Thr Lys Val Glu Val Val Glu Arg Lys 355 360 365 Glu His Leu His Thr Asp Ile Leu Lys Arg Gly Ser Glu Met Asp Asn 370 375 380 Asn Cys Ser Pro Thr Arg Lys Asp Phe Thr Gly Glu Lys Ile Phe Gln 385 390 395 400 Glu Asp Thr Ile Pro Arg Thr Gln Ile Glu Arg Arg Lys Thr Ser Leu 405 410 415 Tyr Phe Ser Ser Lys Tyr Asn Lys Glu Ala Leu Ser Pro Pro Arg Arg 420 425 430 Lys Ala Phe Lys Lys Trp Thr Pro Pro Arg Ser Pro Phe Asn Leu Val 435 440 445 Gln Glu Thr Leu Phe His Asp Pro Trp Lys Leu Leu Ile Ala Thr Ile 450 455 460 Phe Leu Asn Arg Thr Ser Gly Lys Met Ala Ile Pro Val Leu Trp Lys 465 470 475 480 Phe Leu Glu Lys Tyr Pro Ser Ala Glu Val Ala Arg Thr Ala Asp Trp 485 490 495 Arg Asp Val Ser Glu Leu Leu Lys Pro Leu Gly Leu Tyr Asp Leu Arg 500 505 510 Ala Lys Thr Ile Val Lys Phe Ser Asp Glu Tyr Leu Thr Lys Gln Trp 515 520 525 Lys Tyr Pro Ile Glu Leu His Gly Ile Gly Lys Tyr Gly Asn Asp Ser 530 535 540 Tyr Arg Ile Phe Cys Val Asn Glu Trp Lys Gln Val His Pro Glu Asp 545 550 555 560 His Lys Leu Asn Lys Tyr His Asp Trp Leu Trp Glu Asn His Glu Lys 565 570 575 Leu Ser Leu Ser 580 39 294 PRT Deinococcus radiodurans 39 Gln Leu Gly Leu Val Cys Leu Thr Val Gly Pro Glu Val Arg Phe Arg 1 5 10 15 Thr Val Thr Leu Ser Arg Tyr Arg Ala Leu Ser Pro Ala Glu Arg Glu 20 25 30 Ala Lys Leu Leu Asp Leu Tyr Ser Ser Asn Ile Lys Thr Leu Arg Gly 35 40 45 Ala Ala Asp Tyr Cys Ala Ala His Asp Ile Arg Leu Tyr Arg Leu Ser 50 55 60 Ser Ser Leu Phe Pro Met Leu Asp Leu Ala Gly Asp Asp Thr Gly Ala 65 70 75 80 Ala Val Leu Thr His Leu Ala Pro Gln Leu Leu Glu Ala Gly His Ala 85 90 95 Phe Thr Asp Ala Gly Val Arg Leu Leu Met His Pro Glu Gln Phe Ile 100 105 110 Val Leu Asn Ser Asp Arg Pro Glu Val Arg Glu Ser Ser Val Arg Ala 115 120 125 Met Ser Ala His Ala Arg Val Met Asp Gly Leu Gly Leu Ala Arg Thr 130 135 140 Pro Trp Asn Leu Leu Leu Leu His Gly Gly Lys Gly Gly Arg Gly Ala 145 150 155 160 Glu Leu Ala Ala Leu Ile Pro Asp Leu Pro Asp Pro Val Arg Leu Arg 165 170 175 Leu Gly Leu Glu Asn Asp Glu Arg Ala Tyr Ser Pro Ala Glu Leu Leu 180 185 190 Pro Ile Cys Glu Ala Thr Gly Thr Pro Leu Val Phe Asp Ala His His 195 200 205 His Val Val His Asp Lys Leu Pro Asp Gln Glu Asp Pro Ser Val Arg 210 215 220 Glu Trp Val Leu Arg Ala Arg Ala Thr Trp Gln Pro Pro Glu Trp Gln 225 230 235 240 Val Val His Leu Ser Asn Gly Ile Glu Gly Pro Gln Asp Arg Arg His 245 250 255 Ser His Leu Ile Ala Asp Phe Pro Ser Ala Tyr Ala Asp Val Pro Gln 260 265 270 Ile Glu Val Glu Ala Lys Gly Lys Glu Glu Ala Ile Ala Ala Leu Arg 275 280 285 Leu Met Ala Pro Phe Lys 290 

We claim:
 1. A non-naturally occurring nucleic acid molecule comprising a portion which encodes a truncated ultraviolet damage endonuclease (Uve1p), said truncated Uve1p characterized by an amino acid sequence extending from a position between 329 and 479 as given in SEQ ID NO:2 and extending through amino acid 828 of SEQ ID NO:2.
 2. The non-naturally occurring nucleic acid molecule of claim 1 encoding a stable truncated Uve1p characterized by an amino acid sequence as given in SEQ ID NO:2, amino acids 330 to
 828. 3. The non-naturally occurring nucleic acid molecule of claim 1 encoding a stable truncated Uve1p characterized by an amino acid sequence as given in SEQ ID NO:2, amino acids 458 to
 828. 4. A non-naturally occurring nucleic acid molecule encoding a stable truncated Uve1p characterized by an amino acid sequence as given in SEQ ID NO:2, amino acids 518 to
 828. 5. The non-naturally occurring nucleic acid molecule of claim 3 encoding a stable truncated Uve1p, wherein said stable truncated Uve1p is encoded by a nucleotide sequence as given in SEQ NO:3.
 6. The non-naturally occurring nucleic acid molecule of claim 1, wherein said nucleic acid molecule is a vector molecule.
 7. A substantially purified stable truncated UV damage endonuclease (Uve1p) wherein said Uve1p has amino acid sequence as given in SEQ ID NO:2, wherein its amino-terminus is between about amino acid 329 and about amino acid 479, and extends through amino acid 828 of SEQ ID NO:2.
 8. The substantially purified stable truncated Uve1p of claim 7 wherein its amino acid sequence is as given in SEQ ID NO:2, amino acid 458 through amino acid
 828. 9. The substantially purified stable truncated Uve1p of claim 8 further comprising a polypeptide portion identified by an amino acid sequence as given in SEQ ID NO:8 covalently joined at its amino terminus.
 10. The substantially purified stable truncated Uve1p of claim 7 wherein said Uve1p has an amino acid sequence as given in SEQ ID NO:2, amino acid 330 through amino acid
 828. 11. The substantially purified stable truncated Uve1p of claim 10 further a polypeptide portion identified by an amino acid sequence as given in SEQ ID NO:8 covalently joined at its N-terminus.
 12. A composition comprising a substantially purified stable truncated Uve1p of claim 7 and a pharmacologically acceptable carrier.
 13. The composition of claim 12 wherein said truncated Uve1p has an amino acid sequence as given in SEQ ID NO:4.
 14. The composition of claim 12 which is formulated for topical application to skin of a human or an animal.
 15. The composition of claim 12 which is formulated for internal use in a human or an animal. 